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Hi, my name is Mosh, and I'm going to be your instructor in this Python course.In this course, you're going to learn everything you need to get started programming in Python.Python is one of the most popular programming languages, and every day people use it to docool things like automation, they use it in AI, as well asbuilding applications and websites like Instagram and Dropbox. So if you're lookingfor a job, Python is for you. In this course I'm going to teach you everything you need to get started with Python. We're going to talk about all the core conceptsin Python, and then we're going to build three Python projects together.Here's the first project we're going to build. We're going to learn how to create this beautiful websitefor an imaginary grocery store. Here on the homepage we can see allof the products in the shop, and we also have an admin area for managing thestock. We're going to build this using a popular Python framework called Django. Now if you have never built a website before, don't worry, I will teach you everything from scratch. You're also going to learn how to use Python in machine learning, or artificial intelligence. So you will learn how to write a Python programming that will predictthe music that people like based on their profile. Just like how YouTuberecommends videos based on the videos you have watched before. I will also show you python to automate boring repetitive tasks that waste your time. You will write a Python program that will process thousands of spreadsheetsin under a second. I've designed this Python course for anyone who wants to learnPython. If you're a beginner, don't worry, I will hold your hand through this entire course. You're not too old or too young, and Python is super easy to learn. You can write your firstPython program in literally seconds. Plus I'm going to give you plentyof exercises to help you build your confidence writing cool Python programs. My name is Mosh, I'm a software engineer with two decades of experience and I've taught over 3 million people how to code. I'm super excited to be teaching youPython in this course. So I hope you stick around and learn this beautiful powerful programming language. In this tutorial I'm going to show you how to download and install Python on your computer. So the first thing I want you to do,is open up your browser and head over to Python.org. On this page click on downloads, here you can see the latest version of Python currently, at the time of recording this videothe latest version is python 3.7.2. Chances are in the future, when you are watching this tutorial, there is a newer version of Python available, don't worry, all the materials you're going to learn in this course will apply to the latest version of Python as well. So let's go aheadand download Python 3, alright now, look at your downloads folder, here, we should have Python 3 installersimply double click that, if you're on Windows you're going to see this check box here, add Python topython, this is really important, make sure to tick this box, otherwise you're not going to be able tofollow this tutorial. If you're on a Mac, you're going to see an installer like this, with this setup wizard we're going to install Python 3on our computer. So simply click continue, and again, and again, and agree with the license agreement, and install it, this is going to take a few seconds so I'm goingto pause the recording. Alright, we have successfully installed Python 3 on our computer. Let's close this. Alright, next we need to installa code editor, we se a code editor to write our code, just likehow we use Microsoft Word to write documents, we use a code editor to writecode. Now there are so many code editors out there, the one that I'm going to show you in thistutorial is PyCharm. That is one of the most popular code editors for writing Python code. You can get it from jetbrains.com/pycharm. Now more accurately pycharm is considered an IDE, which is short for integrated developmentenvironment. And that's basically a code editor on steroids, it has some additional features that makes it really easy to write code. Solet's go ahead and download PyCharm. Now here on thedownload page, you can see two versions of PyCharm, one is the professional addition which has additional features and you have to pay for them. The other is thecommunity edition, that is absolutely free, and that's what we're going to use in this tutorial. So, go ahead and download this as well.Now, once again look at your downloads folder, once again you should have pycharm so double click this, now if you'rein Windows you're going to see an installation wizard, simply click next, next, nextuntil you install pycharm. If you're on Mac you need to drag and drop this icon onto the applications folder, so drag and drop, alright, now let's double click this to run it, the first time we run pycharm we're going to get this warning, because this is an applicationthat we download from the internet. So let's go ahead and open it, next you're going to see this dialogue box for importing some settings, leave this todo not import settings, it doesn't really matter. Okay,On this page, select I've never used PyCharm you can see some keywordshortcuts that might be useful in the future, just accept this, and down at the bottom, click the next button. And then next again,one more time, and then finally start using pycharm. So here's the main page of PyCharm every time you openit, click on create new project, this is the location for our project, let's call our project HelloWorld. Now before click and create, expand this item here, make sure that base interpreter is set to Python3. Python interpreter is basically a program that knows how to execute Python code, it will know how to interpret or translate Python instructions into instructions a computer can understand. Now, Mac computers, by default come with an olderinstallation of Python, that's Python 2, it's considered legacywhich means it's no longer maintained or supported. So earlier we downloaded Python 3, make sure that this is set to Python 3, if notfrom this list, select Python 3.7. Alright, now let's go ahead and create this project,Now here right click onHello World folder and go to new Python file, call this file app.py. So by convention, all Python files should have thispy extension. Alright, let's go ahead,now let's collapse this project panel by clicking here and write ourfirst python program. Simply type print, print, all in lowercase, open and close parenthesis, and inside these parenthesis, add quotations wecan either use single quotes or double quotes, nowin between the codes write your name. I am Mosh Hamedani, sohere, so this is your first Python programming. With these piece of codeyou can print your name on the screen. Now to run this, goon the top, under the run menu, click run, also note that there is a shortcut associated with this command, whenI program I always use shortcuts because that increases my productivity. So here on a Mac computer, the shortcut is control, option, andR. On Windows it's different. So let's do that, nowit's asking where you want to run this, click on app, down below, you should see this little terminal window, thisis a little window into our program, so here you can see our results foroutput for our program. In the future as you learn more Python, you'll beable to build applications that have a graphical user interface, or gooey. That is a little bit complicated, so for now we're going to use this littleterminal window to see the results of our program. So as you can see my name isprinted here, now as you print code, this window might get in the way soalways resize it or minimize itty putting thisicon here, so this was our first python program. Nowif you didn't see the result I showed you in this video, use the comment box below andtell me what error you encountered, I'll do my best to help you move forward. In this Python tutorial, we're gong to take this program to the next level and make it more interesting. So I'm going to show you how to draw a dog hair. Now as part ofthis tutorial you will learn how Python code gets executed and you will also learnabout a few programming terms. So press enter, and on line 2 write another print statement, so print, open and closeparenthesis, add a quotation, now here you want to draw a dog. So, add an o, that is the head of our dog, followed by4 hyphens. So this is the body. alright, now one more time another print statement withquotations, now we need to draw the legs. So add a space. Follow it by 4 vertical bars. So, like this, so here's a little imaginary dot. Now let's run this program and see what we get. So on the top right corner you should see this play button, click that, there you go, so we have our name and right below that we have our imaginary dog. Now what you need to understand here, is that our python code gets executed line by linefrom the top. So earlier I told you about Python interpreter that is the program that knows how to translate or interpret our Python code into instructions that a computer can understand.So when we run this program by clicking this program here, python interpreter starts executing or running our program line by line from the top. So first it executes line 1, then, moves onto line 2, and so on. So this is how python programs get executed. Now let me show you something cool. Let's add another print statement, with quotations nowin between the quotations, add a star or an asterisk, likethis. Now after the quotation and before the parenthesis, add a space, once again, add an asterisk, space, 10. What is going on here? Well, anywhere we have quotations like here or herewe're defining a string, a string is a programming term which means a series of characters so here we have a string, we also havea string on line 3, as well as line 2 and line 1. Now here, we're multiplying the string by number 10. So this is the multiplication operator, just like the multiplication operator we have in math. So with this piece of code we candraw 10 asterisks on the terminal, let me show you. So let's run thisprogram one more time, there you go. So we have 10asterisks. Now what we have here, this piece of code here, is called an expression. An expression is a piece of code that produces a value. So when Python interpreter tries to execute line 4, first it will evaluate the code that we put in between parenthesis, so we could evaluate our expressions Our expression will produce 10 asterisks and thenthose asterisks will be printed on the terminal. Now as an exercise you can use these print statements to draw another shape, you can draw a heart, a ball, whatever you like. I will see you in the next tutorial. One of the questions I get a lot on my channel ishow long does it take to learn Python and become job ready? Well there is no single answer. It really depends on you and how much effort and commitment you want to put into this. But I would say if you spend 2 hours every dayconsistently, after about 3 months you should be able to write basic python programs, but quite honestly, that doesn't get you a job. In order to get a job, you need to specialize in one area,what do you want to use python for? Do you want to build web applications ordesktop applications? Or do you want to use it in machine learning and artificial intelligence?So whatever you want to do you need to take additional courses. For example if you want to become a web developer in addition to learningPython, you should also learn about html, some css, someJavaScript and Django which is a popular Python framework for building web applications. Learning all these things would take you another 6 months, so in total you need 9-12 months to becomejob ready. At that point you can get a junior developer job with a salary of about 50-60 thousand dollars a year. Now as you work moreas you do more Python projects, your resume starts to build and you can ask for $100,000 a year, or 120,000 dollarsa year, depending on where you are, what company, what geographical area, it really depends, there is no single answer. So are you excited tolearn Python and get started on this career path? If you are, I would encourage youto make a commitment and spend 2 hours every day practicing python. And use the comment box below and let me know why you are learning Python, what do you want to do with it? What's your dream job? I would love to hear your story.In this Python tutorial, you're going to learn about variables, which are one of the most fundamental concepts in programming, they're not specific to Python, they exist in pretty much every programming language out there. We use variables to temporarily store data in a computer's memory. Here's an example, let's type price 10, when Pythoninterpreter executes this code, it will allocate some memory, then it will store the number 10 in that memory, and finally it will attach thisprice label in that memory location. As a metahorimagine we have a box. In that box, we have number 10and price is the label that we put on the box. Now we can use this label anywhere in our program to access the value that we have in that box. This is a very simplified explanation. So now, let's print price on the terminal. Print, now this time we're not going toadd quotations, because if we put quotations here, we will see the text price on the terminal. Now the value of the price variable. So, put it in quotations, and type price, now, let's run this program one more time, there you go. So we see 10, on the terminal. So this is how we define variables, we start with an identifier which is the name of our variable, then, an equal sign and finally a value. Now more accurately, whenthis number 10 is about to be stored in the memory, first it willget converted to this binary for presentation. So this number 10, is in the decimal system which has all the digits from 0 to 9. Computers don't understand all these digits, they only understand 0s and 1s. So when we store the number 10 in the computer's memoryfirst it will get converted to it's binary representation which will be a bunch of 0's and 1's, like 001, 001, whatever I don't know. Then it will get stored in the computer's memory. So,let's take this program to the next level. On the second line we can update the value of this price variable, so we can reset itto a new value like 20, now when we run our program, we should see 20, because as I told you before Python interpreter executes ourcode line by line from the top. So first we set the price to 10, then we reset it to 20, and finally we print it on the terminal, let's run the terminal, there you go, so, we see 20 here, okay? Now thesenumbers that we have here are whole numbers without a decimal point. In programming, we refer to these numbers as integers. But integer is a number without a decimal point. We can also usenumbers with a decimal point for example on line 2, we can defineanother variable called rating and set it to number4.9. Now in programming, we refer to this kind of number as a floating point number of float for short. So we have integers and floats. We can also define a variable and setit to a string, for example, name equals Mosh, we also have another kind of value which is called boolean, which can be true or false. They are line yes and no in English. Here is an example, I'm going to define a variable, is underlinepublished so we use an underscore to separatemultiple words in our variables name. We set this totrue, or false. These areboolean values. now note that Python is a case sensitive language, which means it's sensitive to lower case and upper case letters. So when defining variables we should always use lowercase letters, but here false and true are special keywords in the language, so if we spell it with a lowercase f, Python doesn'tunderstand it. You can see we have a red underline here, which indicates an error. Make sure to spell this with a capital F, or if you want to set this to true, make sure the T is capital, so in thisprogram, you're storing simple values in our computer's memory. Simplevalues can be numbers, which can be integers or floatsor they can be strings or booleans. But in Python we can also store complex values like lists and values. And that's what I'm going to show youin the future. So before going any further, I want you to do a little exercise. Imagine we're going to write a program for a hospital. So we check on a patient named John Smith. He's 20 years old and is a new patient. I want you to define 3 variables here, for his name, his age, and another variable for if this is a new or an existing patient. So pause the video and spend oneminute on this exercise. When you're done, come back, continue and see my solution. Alright, so here we needthree variables, the first one is the patient's name, we set that to John Smith. We can alsocall this full name, these are both valid names for our variables. The second variable is for the age of our patient. So age is 20, and finally we need a variable to tell if this is a new or existing patient. That's where we can use a boolean value. So, we define a variable, is new and we set it to true. So, you have learned how to printmessages on the terminal window. In this tutorial, I'm going to show you how to receive input from the user. So we're going to write a small program that asks the user's name and then we'll print a greeting message customizedfor that user. So instead of print we're going to useinput. Now both these input and print are functions that are built into Python. As a metaphor think of the remote control of the TV. On this remote control we have a bunch of buttons, these are the functions built into your tv, you can turn it on,turn it off, change the volume and so on. In Python we also have functions for common tasks such as printing messages, receiving input, and so on. So we're going to use the input function, now whenever wehave these parenthesis, we're going to say we're calling or executing that function, it's like pressing a button on a remote control. So we'regoing to call the input function and in between parenthesiswe want to add a string to print something on the terminal, what is your name? With a question mark followed bya space. You will see why in a second. So this input functionwill print this message on the terminal, and then it will wait for the user toenter a value. Whatever the user enters this input function willreturn. So now we can get that value and store it in the memory using a variable. So we get the result and put it in a variable called name. Okay? Now on the second linewe want to print a message like Hi John or Hi Mosh or whatever, so, print, quotations Hi with a space,now after the quotation we want to dynamically printwhat we have in the name variable. So we hada plus sign and then name. So here we haveHi which is a string, we're concatenating orcombining the string with another string, that is what we havein the name variable. So here's another example ofan expression. Remember what is an expression? It's a piece of code thatuses a value. So this expression concatenates or combines 2 strings. Let's run this program and see what happens. So runokay, here is a question, what is your name? Mosh, now note that earlier we added a space after the question mark, wedid this, so here in the terminal window the cursor isseparated from the question mark, otherwise it would be so close. So let's typewhatever here, plus enter, now we get this message, Hi, Mosh. Now here's a little exercise for you. I want you to extend this programand ask two questions. First all the person's name and thentheir favorite color. And then print a message like Mosh likesblue. So pause the video, do this exercise and then come back and continue watching. Alright, so here's the first question right after that, all the input functions one more time, this time we're going to ask a different question. What is your favorite color? Now, we get the new value and store it in the variablecalled color, or you could call it favorite underline. color. Either works. And finally we're going to changewhat we pass to the print function, so first we print the name then we concatenate this with a string, here we're going totype likes, we also put one space before and after likes, and once again we concatenate this. With the favorite color. So, favorite color, now let's run this program, so what is your nameMosh enter, favorite color, blue, enter, we get this message, Mosh likes blue. Hey guys Mosh here, I just wanted to let you know thatyou really don't have to memorize anything in this course because I've put together a cheat sheetwith summary notes. So you can quickly review the materials in this course. The link is below this video. So I have done my best to createthe best possible Python course on Youtube. And I really appreciateit if you support my hard work by liking this video and sharing it withothers, so they can learn as well. And be sure to subscribe to my channel, for more tutorials like this. Alright, now, let's move onto the next tutorial. In this Python tutorial, we're going to write a program that will ask the year that we were bornin, and then it will calculate our age and print it on the terminal. So, let's start with our input function, input let's print birth here, followed by a colon, and a space. Now let's get the return value and store it in a variable, called birth year. So as I told you before, we use an underscore to separate multiple wordsNext, we need to calculate the age, so we define anothervariable called age, and here we do some basic math, currently we are in 2019, so let's write an expressionlike this. 2019 - birthyear. Now finally let's print age on the terminal. Let's run our program and see what happens. So, my birth year is 1982, enter, oops, we got an error, what is going on here? So whenever you see this message, that means there is something wrong with your program. With the informationhere, we can find exactly where the error occurred. So, next to the file you can see the file that generated this error, in this casethat is app.py. Socurrently our program only has a single file, but real complex programs oftenhave hundreds or even thousands of files. So in this file, on line 2, this is where we got this error, and rightbelow that we can see the piece of code that generated this error. So that is where we're calculating the age, and right belowthat you can see the type of error. In this case, we have a type error, and here's themessage. Unsupported operand types forsubtraction. Int and str.So int is short for integer and that represents a whole number and str is short for string, so here we're subtracting a string from an integer, and Python doesn't know what to do with it. Let me explain. So I'm going to close the terminal window. So afterthe first line we executed we have this birth year variable set to a string, so whatever we type in the terminal is alwaystreated as a string, even if you type the number, in other words, when we run this program, this birth year variable will be setto a string, with four characters. 1982. This string is different from the actual number1982. One is an integer and the other is a string. Right? So, back to line 2, where thiserror occurred. At run time, which means when we run our programthis expression on the right side of the assignment operatoris going to look like this. 2019 - string 1982. Python doesn't know how tointerpret or how to evaluate this expression. To fix this problem we need to convert this 1982 into an integerand then we'll be able to subtract it from 2019 and that is easy. So far you have learned about two built in functions one is print the other is input. We have a few other functionsfor converting values into different types. So we have int for converting a string into an integer, we also havefloat for converting a string into a float, or a numberwith a decimal point. And we also have bool for converting a string into a boolean value. So to fix this problem, we need to go back on line 2, and pass this birth year variable to the int function like this.int parenthesis, like thisso we pass this string to the int function, int will convert it into an itnegerand then Python interpreter will be able to evaluate this expression. Now let's run this program one more time, so birthyear is 1982 enter so I am37 years old. In Python we have a useful functionfor getting the type of variables, for example, let's print the typeof birth year, so right after line 1, let's print, now here we're going to call another built in function, called type, and now let's pass birth year, okay, now similarly after line 3, let's also print the type of age, soprint type of age. Okay? So let's run our program, so birth year one moretime, 1982, okay, here's the resultso the type of birth year as you can see is a classof str or strings, we look at classes in the future sofor now don't worry about them, and also below them you cans ee the type ofthe age variable is int or integer. Sohere's what you need to take away. Whenever you use the input function, you always get a string, so if you're expecting a numerical valueyou should always convert that string into an integer ora float. So here's a little exercise for you. I want you to write a program ask the user their weight and then convert it to kilograms and print iton a terminal. So pause the video, do the exercise and when you're ready come backto watch it. Alright so let's use our input function and askfor the weight in poundshere we get the weight in lbs or poundsnow we need to convert this into kilograms, it's very easy sowe defined another variable weight kg we set this to weight lbstimes 0.45. And finally let's print weight underlinekg. Let's run this Python program and see what happens. Somy weight is 160, alright once again we got an error, can't multiply sequence by non int of typefloat. So as I told you before, this input function returnsa string, so we cannot multiply a string by a float. Python doesn't know what to do with it. So in this case, we should convert this numberby an integer or float and then multiply by 0.45. So let's call the int function. And pass weight underline lbs.And run our program one more time, 160okay, so I am 72 kg's. In this tutorial, you're going to learn more about Python strings. So I've defined this course variable and set it to Python for beginnersnow earlier I told you you could use both single and double quotesto define a string, but there are times you have to use a specific form,otherwise you're going to run into issues. Here's an example. Imagine you wanted tochange this string into Pythons course for Beginners. So we want to add an apostrophe, like this, Course for Beginners. You can immediately say this is goingcrazy, because our string starts here and then terminates here, all these characters that we have here after the second apostrophePython interpreter doesn't know what they are. So to solve this problemwe need to use double quotes to define our string so we can have a single quote in the middle of the string. So let's change thisto double quotes, now you can see it adds another double quote to close it, you have to manually remove this, and also one more timeat the beginning of the string, we need to add another double quote. Nowyou can see error is gone, so if you print course we see Python course for beginners. Beautiful. Now let's say we don't want this apostrophe here, so we havePython for Beginners, but we want to put Beginners indouble quotes. Once again, if you add a double quote here Python interpreter getsconfused because it assumes the second double quote indicates thatend of the string, so it doesn't know what these characters are, so to solve thiswe need to change our double quotes to single quotes like this. And then we can add double quotes in the middleof the string. Now let's run this program, there you go. So we get Python for Beginners. So these are the casesfor using single or double quotes. Now in all the examplesI've shown you so far we only deal with short strings, but what if you wanted to define a string that is multiple lengths? For example, what if you wanted to define a string for the message that we send in an email. In that case we need to use triple quotes. So. We delete this. Now we add three quotes, so 1, 2, 3, there you go, So, we have three quotes to start our string and three to terminate it. Again these quotes can be single or double quotes. Okay? Now, with this we can define a string that spans multiple lines. For example, we can say Hi Jon here is our first email to you. Thank you, The Support Team. Like that.Now, let's run this program and here's theresult. So, we get this beautiful multi linestring. Now let's change this back to something simple so, we can look at other characteristics of strings and Python. So I'm going to use single quotes and set the course name to Pythonfor Beginners. Now here we're going to use square brackets to get a character and a given index in this string. Let me show you. So to get the first character we use square brackets and type 0. So the index of the first character in the string is 0. In other words, this is how Pythonstrings are indexed. 0, 1, 2, 3, 4, etc. So the index of the first character is 0, the second character is1, and so on. So let me delete this and run this programwe get p. We can also use a negative index here. And this is one of the features that we don't have in other programming languages as far as I know. So we have negative index we can get the charactersstarted from the end. So if I pass negative 1 here, Assuming that 0 is the index of the first character negative 1 is the index of the last character. So when we run this program we should see s. Let's run it, there you go,we get s, if we pass negative 2, this will returnthe second character from the end. Let's run it one more time, now we get R because that is the second character from the end. Okay? So place close attention to this square brackets syntax because quite often it's the topic for online Python tests or university exams, so if you're preparing for a python test, make sure to watch this tutorial one more time and understand exactly howthis square brackets syntax works, we can also use a similar syntax to extract a few characters instead of 1 character. For example, if we type 0, colon 3, Python interpreter will return all the charactersstarting with this index all the way to thissecond index, but it does not return the character at this index. In other words, back to these indexes so you have 0, 1, 2, 3, and so on. When you run this program. Python interpreter will return the characters starting from theindex 0 all the way to index 3, but excludes the character and index 3, so when we run this Python program we're going to see pint (?). Let me show you, so we're going todelete this line, run this program, there you go. We get pint. Now here we also have default values forthe start and end index. So if we don't supply the end index, Python will return all the characters to the end of the string. Let's take a look. So run this program, there you go,Python for Beginners. But if you change the start index to 1, this will exclude the first character so when werun this program, we see ython so p is removed. Okay? Now similarly we have a default value for thestart index, so if we don't supply the start index but add an end index like 5. Python interpreter will assume 0 as the start index, so, let's runthis program, there you go, we get pytho. Now what if we leave both the start and endindex? Well, I told you? Now in this case 0 will be assumedas the start index, and the length of the string will assumeas the end index. So with this syntax, you can basically copyor clone a string. In other words, if I defineanother variable here, let's call it another and set it to course square brackets with just a colon, now this expression willreturn all the characters in the course variable sovariable will be copy of our first variable. Let's take a look, so, let's print another, and load ourprogram there you go, we get Python for beginners. So once againthe square bracket syntax is pretty important if you're preparing for onlinepython tests, or college exams, make sure to watch this tutorial again. Now here's a little exercise for you. I'm going to delete all this code define a variable, called name, and set it to Jennifer. Now when we print name of 1: negative 1what do you think we're going to see on the terminal? I want you to use your knowledge to tell what we're going to see on the terminal, we're now running this program. Sopause the video, think about it for a few seconds, then come back and continue watching. So this expression will return the characters starting from index 1 which is the second characterall the way to the first character from the end, but excludingthe character at this index. In this case, the first character from thein is r, so r will be excluded, in other words we're going to seeall the characters starting from e all the way to the second e. Let's take a look. So I'm going to run this program there you go. This is what we get, I hope you guessed it right. In this tutorial, we're going to look at formatted strings in Python programming language. Formatted strings areparticularly useful in situations where you dynamically generate sometext with your variables. Let me show you. Let's say we have two variables first name and last name. So first we set this toJohn, and last we set this to Smith. Now it's betterto call these variables first name and last name, because they're moredescriptive. But here I'm using shorter names because I want you to see the entire code on display screen. So let's say with these two variables, we want to generatesome text like this. Jon, in square brackets Smith is a coder. Let's say we want to print this onthe terminal. How do we do this? Well, we define another variable like message, now here we add the first name, now we need to concatenate this, with a string that contains a space and a square bracket next we need to add a last name, then we need to add a string that containsthe closing square brackets followed by is a coderokay? So, then, if you print message and run this program to see John Smith is a coder, right? Now, while this approach perfectly works, it's not ideal because as our text gets more complicated it becomes harder tovisualize the output. So someone else reading this code, they have to visualize all the string concatenations in their head. This is where we useformatted strings, they make it easier for us to visualize the output. So, I'm going to define another variable, let's saymsg short for message, and set this to a formatted string. A formattedstring is one that is prefixed with an f. So f, quotes. Now in between the quotes, first we want to addthe value of the first name variable, so, we add curly braces and here we type first.Next we add a space, we add our square brackets, in between the square brackets, we want to display the last name so once again we add curlybraces, and type last, and finally here we type is a coder. So this is what we call the formattedstring. With these curly braces, we're defining place holdersor holes in our string, and when we run our program these holes will be filled with the value of our variables. So here we have two place holdersor two holes in our string. One is for the value of our first name variable and the other is for the value of the last name variable. But compare this formatted string with string concatenation. With this formatted string we can easily visualize what the output looks like, right? Now let's print this otherterminal to make sure we get the same exact output. So, let's print messagethere you go. So JonSmith is a coder. So to define formatted strings, prefix your strings with an F and then use curly braces to dynamically insert values into your strings. In this Python tutorial, I'm going to show you some really cool things you can do with Pythonstrings. So let's start by defining a variable, course and we set that to Python forbeginners. Now to calculate the numberof characters in this string, you can use a built in function called len.So len we give it this course variable, and then, we can print the result. Let's run this program, so as you can see we have 20 characters in this string, this is particularly useful when you receive input from the user. For example you havenoticed that when you fill out a form online, each input field often has a limit. For example, you might have 50 characters for your name, so using this len function we can enforce a limit on the number of characters in an input field. If the user types in more characters than we allow, we can display an error, now, this, len function is another function built into Python, it's a general purpose function, so it's not limited to counting the number of characters in a string, in the future when we look at lists, I want to show you that we can use thisfunction to count the number of items in a list. So it's a general purposefunction. Now we also have functions specifically for strings for example we have functions for converting all these characters to upper caseor lower case. To access these functions we use the dot operator. let me show you. So first we type course, then dot look these are all the functions that are specific to strings. Now in more accurate terms, you refer to these function as methods, this is a term in object oriented programming that we want to look at in the future, but for now, what I want you to take away,is that when a function belongs to something else, or is specific to some kind of object, we refer to that function as a method. For example, here we have this function, upper, for converting the string into upper case, now more accurately because this functionis specific to a string, we refer to this as a method. In contrastlen and print are general purpose functions, they don't belong to strings or numbers or other kinds of objects. So this is the difference between functions and methods. Now let's take look at thisupper method. So, let's print the resultsand we run our program, there you go, you get all these characters displayed in uppercase. Now note this method does not change or modify our original string, in fact it creates a new string and returns it. So, if we print our course variable right after wecall the upper method, we can see that our course variable still has it's original form, so let's run this program one more time, there you go. Look, here is our original course variable, it's not modified. Now similar to the upper method we have another methodfor converting a string into lower case. So let me show you. Print, course.lower. Now, let's run the program, so on the second line you can see, all characters are in lower case. Now there are timesthat you want to find a character or a sequence of characters in a string. In those situations you can use the find method. So let me deletethese few lines. Call course.find here we pass a character, let's say p, and this will return the index of the first occurrence of that character, let me show you. So let's print the resultwe get 0, because the index of the first capital p in the string is 0. As another example, if we pass a lower case o here, let's see what we get, we get 4 because the index of this o here is 4. Now note that thefind method is case sensitive, so it's sensitive to lower case and and upper case characters. As an example if you pass an upper case here and run this program, we get negative 1 becausewe don't have an upper case o anywhere in this string, okay?We can also pass a sequence of characters, for example, we can passbeginners with a capital Blet's run this program, we get 11 because beginners starts with index 11, now wealso have method for replacing a character or a sequence of charactersand that is called replace. So let's change find to replace let's say we want to replace beginners withabsolute beginners, so we add a comma to pass a second valueto this function, or more accurately this method. We add a string, here I'm going to pass absolute beginners. Okay, now let's run this program,so, we get python for absolute beginners. Again, this method like the find method is case sensitive so if you pass beginners all in lowercase, this method isnot going to find this exact word in our string, so it's not going toplace it with absolute beginners. Let's take a look. So I'm going to run the programOne more time, look, we still get python for beginners. We can also replace a single character, for example we can replacecapital p with let's say capital j. Now when we run this program we getjython for beginners. So these are the find and replace methodsand one last things I want to show you in this tutorial. There aretimes that you want to check the existence of a character or sequence of characters in your string. In those situations you use the in operator, so let's say you want to know if this string contains the word python. We can write an expression like this. Stringpython space in space course. So we're checking to see if python is incourse variable. And this is an expression that produces a booleanvalue, and I get true or false, so we refer to this expressionas a boolean expression, now if we print this on the terminal, we should get true, and by the way I'm going to delete the second line, we don't need it anymore, so run the program we get true, but if I change this capitol p to a lower casep and run the program we get false because we don't haveis exact sequence of characters in our strings. Now note that the difference between the in operator and the find methodis that our find method returns the index of character or sequence of characters but the in operator produces a boolean value. Do we have this or not? So that's the difference. Now let's recap all the cool things you learnedto do with strings in this tutorial. We can use the len functionto count the number of characters in a string, this is the generalpurpose function built into python, we also have specific functions for strings which we refer to as methods, these include upper for converting a string into uppercaseyou also have lower and title methods, you learn about the find method which returns the index of a character or sequence of characters, we have the replace method for replacing characters and words in a string and finally you learned about the in operator. So some characters in a string. So, you have learned that in Python programming language you have 2 types of numbers, integers which are whole numbers like 10, they don't havea decimal point, and floating point numbers or floats.Which are numbers with a decimal point. Now in this tutorial you're going to lookat the arithmetic operations supported in python language these are thesame arithmetic operations that we have in math, we can add numbers, multiply them and so on. So let's look at a few examples, we can print, 10 plus 3, so this is the addition operator, we also have subtraction, we have multiplication, we have two kinds of division, here's one with a forward slash, let's run this program and see what we get.we get a floating point number. But we also haveanother division operator for getting an integer. So if we add another slash here and run this program we get an integer. We have another operator called modulis (?) which is a percent sign.And this returns the remainder of the division. So when we run this program we should get 1, there you go. Andone last operator we have here is exponent which is the power. So, that is indicated with 2 asterisks and this will return 10 to the power of 3. So let's run this program we get 1000 so these are the arithmetic operators in python programming language. Now for all these operators that you learned we have an augmented assignment operator. That isvery useful, let me show you. So let's say we have a variable called x we set it to 10, now we want to increment this by3, we'll have to write code like this. X we set this tox plus 3. So Python interpreter will add 10 to 3, the result is 13, and then it gets stored into x again. So when we print x we should see 13, there you go. So this is how you can increment a number, right? Now augmented assignment operator isa way to write the same code but in a shorter form. Thisis how it works. We type x plus equals 3. What we have on line 3 is exactly like what we have on line 2. So this is what we callthe augmented assignment operator we have augmented orenhanced the assignment operator. Now in this particular case we are incremented a number using the augmented assignment operator,but we can also subtract or multiply a number by a given valuefor example, let's delete what we have on line 2, we can type subtract equals 3. So here we subtracted 3 from x. When we run this program we should see 7, there you go. Now let me ask you a question, I'm going to clear all this code here todefine x and set it to 10 plus 3times 2. What do you think is the result of this expression? this is a very basic math question that unfortunately a lot of people fail to answer. The answer is 16. Because in math we have thisconcept called operator precedence which means the order ofoperations. So the multiplication operator has a higher precendence which means it's applied first which means 3 x 2 is executed first, the result is 6 and then its added to 10, that's why x showed up as 16 afterwe run this code, let's verify that. So, print x run the program, x is 16. So this is what we calloperator precedence, it's just a basic math concept. It's not about python programming language. So all the other programming languages behave the same way, so here's the order, first we have the exponentiation which is the power, like 2 to the power of 3, then we have multiplication or division and finally we have addition or subtraction.This is the order of operations. Let me show you another example. Here I'm going to add the exponentiation operator, so, 2 to the power of 2. Once again, what do youthink is the result of this expression? Pause the video and think about it for a few seconds. The answer is 22. Because the exponentiation operator takes precedence, so first 2 to the power of 2 is executed, the result is 4, then 4 is multiplied by 3, that is 12, and finally 12 is added to 10. So x should be 22. So let's run this program and verify this. So I'm going todelete these lines here. Run the program, there you go. X is 22. Now let me bring back these rules here. We can also use parenthesis to change the order of operations so if we have parenthesis we always takes priority. In this case we can add parenthesis around 10 + 3, so this piece of 3 will be executed first, the result is 13, then the exponentiation operator will be executed, so 2 to the power of 2 is 4, and finally 4 is multiplied by 13. Now here is a little exercise for you. I'm going to set x to parenthesis 2 + 3 x 10 minus3. What is the result of this? Pause the video and think about it for a few seconds. So you learned that parenthesis always overrides the order, so this piece of code is executed first. The resultof these 5. Then, between the multiplication and subtraction, you know that multiplication takes precedence. So next, 5 will be multiplied by 10, the result is 50 and finally we have subtraction. So 50 minus 3 will be 47. Let's verify this, print x, run the program there you go, I hope you guessed it right. So this is all bout operator precedence, it's a very important topic and I see it quite often in Python tests. So if you're preparing for a Python testmake sure to watch his tutorial one more time. In this tutorial, we're going to look at a few useful functions for working with numbers let's start by defining a variable like x and set it to 2 .9. Now to round this number we can use the built inround function, so we call the round function, give it x, and then print the result. Let's run this program so, we get 3, we have another useful built in function called abs which is short for absolute, and this is the absolute function we have in math, we give it a value and it always returns the positive representation of this value, even if the value is negative.Here's an example. Let's call the abs function and give it negative 2.9 When we run this program we're gong to see 2.9 on the terminal. So let's go ahead there you go. So absolute always returns a positive number. But technically in Python we have a handful of built in functions for performing mathematical operations, if you want to write a program that involves complex mathematical calculations, you need to import the math module.A module in Python is a separate file with some reusable code. We use these modules to organize our code into different files. As a metaphor think of a super market. When you go to a super market you see different sections for fruits and vegetables, cleaning products, junk food and so on. Each section in the super market is like a module in Python. So in Python we have this math module which contains a bunchof rustable functions for performing mathematical calculations. So, let me show you how to use this module. On the top we type import, math, all in lowercase with this we can import the math module. now math isan object like a string, so we can access it's functions or more accurately it's methods using the dot operator. So if you type math. look these are all the mathematical functions available in this module. For example you can call theseal method to get the sealing of a number. So if you pass 2.9 hereand then print the result we should see 3. Let me delete all this other code here. Alright, let's run this program there you go. So we get 3. Another useful method is thefloor method, so let's give that a try, floor of 2.9. What do you think we're going to get? We get 2. Now there are so many functions built in this module and we don't really have timeto go through all of them. But let me show you how we can learn about them on your own. Open up your browser and search for Python 3math module. Make sure to add the version python 3. Because the math module in python 2 is slightly different from the math module in python 3. So python 3 math module, now here you can see the documentation of this kind of module let's go let's have a look, if you scroll down, we can see the list of all the functions and their explanation. So as an exercise I encourage you to have a quick look at thisdocumentation. See what functions are there for you in case you need them. In this tutorial, I'm going to talk to you about if statements in Python if statements are extremely important in programming and theyallow us to build programs that can make decisions based on some condition. So if some conditions are true we're going to do certain things, otherwise we're going to do otherthings. Here's an example. Over here I've got this text file witha bunch of rules for our program. If it's a hot day, perhaps we want totell the user it's a hot day, so make sure to drink plenty of water. Otherwise, if it's cold, so here's another conditionif this condition is true we're going to tell the user it's a cold day so where warm clothes. And otherwise if it'seither hot or cold, we want to tell the user it's a lovely day. So let me show you how to write a program that simulates these rules. So, back to our program here, we start by defining a boolean variable is underline hot. We set this to true. Next, we add an if statement, so if, herewe need to add a condition, in this case we're going to use our boolean variable. So, is underline hot. So if this values to true. Then we're going to do certain things. In this case, we want to tell the userhey it's a hot day, drink plenty of water. So, back to our program after our condition we add a colon, now, note that when I press enter pycharm automatically indents our cursor. Now any code that we write here will be executed if this condition is true, otherwise it will be ignored. Hereis an example. Let's write a print statement, here I'm going to usedouble quotes because I want to use an apostrophe in our string. So, it's a hot day. Now let's press enteryou can see the cursor is still indented, that means we can write more code that we executed if this condition is true, in this case let's say we don't want towrite any extra code, so to terminate this block we need to press shift and tab, now the cursor is at the beginning of the lineso lets write a print statement with a message likeenjoy your day. Now when we run this program, becausethis condition is true, you're doing to say this message followed bythis second message, take a look, so run, there you go, it's a hot dayenjoy your day. But if I go over here and change this boolean value to false and run the program again, ourfirst message disappears and we only see the second message, enjoy your day. So this is how if statements work. Now backhere we can add another print statement let's saydrink plenty of water. Now because this spirant statement is also indented it will beexecuted if this condition is true. So I'm going to revert is hot to true and run the program one more time. There you go, so it's a hot day, drink plenty of water, and enjoy yourday. Alright now let's add a second rule here, ifit's hot we're going to execute these two lines, otherwise if it's not hotwe want to print a different message. So here we are moving an indentation and typing els colon. Now when we press enter once again our cursor indented so the code that we write here will be executed if thiscondition is not true. So here we can print it's a cold day, print, where warm clothes. Now let's run our program one more time. So we get the message about a hot day followed by enjoy your day. You don't see any messageabout a cold day. Now if we go back here on the top. And change this boolean value to false and run our program we see different set of messages. It's a cold daywear warm clothes and enjoy your day. But there's a problem with our program. If it's not hot it doesn't necessarily mean that it's cold, it meansit's a lovely day. So the absence of heat doesn't mean its cold. Back to our conditions, here on line 4 we have this rule that says if it's a cold day, then print these messagesotherwise if it's neither hot or cold say it's a lovely day. So, to implement this rule we need to go back and put py and define another variable. So let' say is underline cold we set this totrue. Now here we need to add a second condition. So afterour first if statement, we can use an el if statement to define a second condition. So here's how it works. So, el if which is short for els if orotherwise if, now here we add another condition, so, is cold So if t's cold you want toexecute these few lines. So let's cut thesefrom here, and move them under our second condition and finally if none of these conditions are true, you want to print a different message. It's a lovely day. So, right now, is hot is false, is cold is true, so when we run this program, python interpreter is going to execute the first if statement, in this case because our condition is false, these twolines will be ignored, then Python interpreter will look at line 7, it will evaluate this condition, in this case iscold is true so we're going to see these two messages on the terminal. Now, in this case, because one of these conditions was true, this els statementwill be ignored, so we are not going to see this message, and finally as before, we are always going too see this message. So let's run ourprogram, there you go. it's a cold day, where warm clothes and and enjoy your day. Now, back to the top, if we change is cold to false it's neither hot nor cold so it's going to be a lovely day.Let's run the program, and here you go, it's a lovely dayenjoy your day. So these are the basics of using if statements. As you can see they are very useful in programming and with thesewe can build all kinds of rules into our programs. Okay here's anexercise or you. Imagine the price of a house is 1 million dollars. Now if the buyer has good credit, they will need to put down 10 percent of the price of this property otherwise they need to put down 20 percent write a program with these rules an display the down payment card for a buyer with good credit. You will see my solution next. Alright let's define a variable for the price of this house so price we set this to 1 million so 1 with 6 0s. Next we need a variable to tell if this buyer has good credit so has good credit, and we set this to true, now we need an if statement so if has good credit has true colon, here we need to calculate a down payment sothe down payment should be equal to0.1 x the price. That is 10 percent of the price of thisproperty. Otherwise colonthe down payment should be 0.2 times price. Now finally we remove theindentation and print here we can use a form of valid string, first we add a label, down payment colon and right after that we add a placeholder or a hole for our down payment variable. So curly braces down payment. Let's run thisprogram, so down payment for a buyer with good credit is 100,000 dollars. Now let's improve this by adding a dollar sign before this number. So back to our formatted string,just before the curly brace I'm going to add a dollar sign let'srun this one more time, that is better. In this tutorial I'm going to talk to you about the logical operators within Python.We use these operators in situations where we have multiple conditions. Here is an example. Let' say we're building an application for processing loans. If an applicant has high income and good credit, then they're eligible for a loan. So in this example we have two conditions, one is having high income and the other is having good credit. So if boththese conditions are true, then the applicant is eligible for a loan.So this is where we use the logical and operator. We use this operator to combine two conditions, and by the waythis is not specific to python programming language, pretty much any programming language that supports if statements also supports the logical operators. So, back to our program, let's define two variables, has high income, we set this to true. And another one has good credit, we also set this to true, now our if statement if has high income has true, and has good credit is also true, then we're going to print eligible for null. So this is where we're using the and operator. So if both these conditions are true then this message will be printed. If one of them is false, we're not going to see this message. Let's try this out. So I'm going to run this program so we see it eligible for loan, but if we change either of these conditions to false, and run the program again look, the message disappears. So this is the logical and operator. We also have thelogical or, and we want to use that in situations where we want to do certain thingsat least one of the conditions is true, for example let's change the rule for this program, such that if the applicant has high income, or good credit, then they're eligible for a loan, so if either or both these conditions are true then the candidate iseligible. Now back to our program we can implement this rule by using the logical or operator. So we simply replace and with or, now when we run this program we're going tosee this message because at least one of our conditions is true, let's take a look. So the applicant is eligible for a loanfor a loan because they have good credit. If you change this to false but set the other condition to true, we stillsee the same result, but if both these conditions are false then we're not going to see this message anymore. So this is the difference between these operators. With the logical and operator both conditions should be true, with the logical or operator at least one condition should be truewe also have another logical operator called notand that basically inverses any boolean value we give it, if we give it, we give it a true boolean value it converts it to false. For example let's make up a new room, if applicant has good credit and doesn't have a criminal record thenthey're eligible for a loan. Let me show you how to implement this. So, we go back to our program, in this example we don't need a first variable for let's delete that. Let's set this variable to truewe also define another variable like has criminal record. We set this to false. Now, we want to check to see if this applicant has good credit and nota criminal record. This is where we use the not operator. So, if they have good credit, and not criminal record. So, in this example, has criminalrecord is set to false, when we use the not operator thisbasically gets changed to true, so we have two conditions that are true. Here's ones and here's another one. So our applicant iseligible for a loan. And when we run this program we seethis familiar message. Howeverif an applicant has a criminal record, so let's change this to true, now when we run this program we can see our applicant isnot eligible because when we apply then operator on thisvariable, we'll get false. So true changes to false. And we'll end up with two conditions, one that's trueand the other is false. And that's why this message isnot printed. So this is all about the logical operators inpython. In this tutorial I'm going to talk to you guys aboutcomparison operators in Python. We use comparison operatorsin situations where we want to compare a variable with a value, for example, if temperature is greater than 30, thenwe want to print it's a hot day. Otherwise, if it's lessthen 10, it's a cold day, otherwise it it's neither hotnor cold. And by the way I'm taking about celsius, not farenheit. So, to build these rules into our program, we need to use comparisonoperators. Back to app.py, I define thistemperature value, let's write an if statement, if temperaturenow we want to check to see if this is greater than 30, so we use the greater than operator. If this is greater than 30, we want to print it's a hot dayotherwise, let's just print it's not a hot day. Now, when we run this program, we're going to see this second message because 30is not greater than 30. So our fi