Learn Python Through Real-World Examples

welcome to the course this is the very first lecture and in this lecture I'll give you a short introduction to this course I'll tell you what the course covers how how it is structured I'll mention the different types of content that you'll find here and I'll let you know what to expect in terms of goals you want to reach so the course is structured into several sections and sections are nothing more than logical groupings of several lectures uh now for instance you are at lecture one of section one and so in the first section I'll mention a few facts about python then I'll show you how to install python version three and where to write and execute python code then in section two you will learn how to declare and use variables you will also learn how to use numbers and strings uh which are two basic data types in Python then once you have learned variables numbers and strings in Section 3 you will be ready to write some tiny programs using conditionals also in section three you will learn how to write your own functions and once you have a good grasp of of custom functions you will already start to feel confident in writing lines of code uh then we will jump over to section four where you'll learn some more complex data types that are lists to both sets and dictionaries uh then you'll practice these data types as you learn how to perform iterations using the for Loop in Section Five I'll go over to some more practical comp Concepts where you will learn how to create and open files and write content inside these files in in that section you will also be practicing iteration combined with the file handling techniques and then I'll explain to you all the functionalities that I mentioned above while typing code executing and getting the code output however some things you'll be able to understand by yourself by completing the exercises which you will find as you progress through the course uh that's an excellent technique because it will keep you very active and will help you code independently with confidence there are also interesting quizzes in the course that will continuously test your knowledge and once you have learned all the building blocks of language I'll show you the way how you can apply that knowledge for making python programs that will solve your problems in your specific professional field so I'll show you how to look for special Python functionalities and how to use them for programming with python and moreover we will be building some real world small programs and then I'll ask you to improve those programs so that you understand them better and learn how to do them by yourself and lastly I'll show you how to make your python programs more user friendly so that other people can also execute them and to sum it up regardless of the field of Technology where you're planning to use Python this this course will get you up and running fast with python so let's roll and see you in the next lecture so in this first lecture I'm going to tell you a few words about python such as what python is what it can do uh What fields oft technology can python be used for uh where python stands among the other programming languages and how python has become so popular so python is definitely not a large heavy boded non venous constrictor snake it is a powerful high level programming language intended for general purpose so a higher level language means a language that enables the development of a program in much simpler way as opposed to lowlevel programming languages python as many other programming languages is a high level programming language so with python you'll never have to think about lowlevel languages I said earlier that python is a general purpose language and it release the languages used in many fields according to the official python web page these fields are web and internet development scientific and numeric education desktop graphical user interfaces and software development and as you see python covers probably everything that can be done with with a programming language python is a simple readable and efficient language if you were to create a program uh you would create that program with with much less lines of code using python that using uh the C language for example and on top of that those few lines of python code would be more readable than the C code and all that makes python a very enjoyable programming language and I bet you'll enjoy whenever you'll be given a new problem to solve with python python was conceived in the late 1980s and python 2 version two was released in 2000 and Python 3 was released in 2008 Python 3 is the latest uh release currently uh there is a version we are using in this course today python is one of the most popular programming languages and its popularity is increasing so how did python become so popular well I already mentioned readability so that's one of the reasons why why people like and choose to program with python uh but also Google is using Python and YouTube was written in Python also python has a great community that is always ready to help other reasons for the popularity of python can be specific for certain communities for instance python has a great support for uh for data analysis and you can do whatever you like with to your data so if you're taking this course uh it's probable that you have decided to Learn Python 4 handling data and I'm sure we'll learn a lot and we'll have a lot of fun programming with python I believe all you need is time management so welcome again to this course and talk to you in the next lecture welcome to this new lecture and I assume you have already taken the previous lecture where I talked about python in general and the other lecture as well where I showed you how to download and install Python and the spider environment and the IPython console as well in this lecture I'll tell you a few things about the spider environment as that will be the environment from where I'll be writing and executing the python code so the platform we we're looking at is spider and spider stands for Scientific Python development environment don't get scared by the name spider is just an environment where you write and run python code so spider provides an an editor here on the left and an interactive shell here on the right the interactive shell is provided by IPython so IPython is an enhanced shell where you write and run python code so IPython is like the basic shell that you you can access through your command prompt but with some added capabilities uh that uh we will discover together as we move through the course you can also access IPython 3 your command line uh by just typing IPython and you get the same console with the same functionalities as the one you have in spider but I would suggest you use the IPython through through spider because you have everything inside one single environment so to write scripts of code you should use the editor here on the left and I have another very short lecture where I'll teach you how to run scripts of code to program interactively you use the shell on the right so programming interactively means uh writing and executing single lines of code uh this is done mostly when when testing and where you're not intending to save your your scripts of code for instance let's instruct python to print out some text for us so the function that prints out text is print and the text we want to print is displaying some text and so we get the text displayed as soon as we hit enter on the keyboard so that's what I refer to as interactive programming uh you can open multiple shells or consoles here if you like but normally you'll not have to do so uh you can choose to show or hide these two panes by going to view panes and then click the pane you want to show or hide so if I check the editor the editor will will hide and I have a full view of the iPod and shell you could also modify the way your spider looks by going to tools and then to preferences and here you have quite a lot of displaying options that you can play around with for example I may want to remove the header of the IPython console so I go to IPython and uncheck that option now the next time I open spider or even if I start a new console now the header will have disappeared there are also options that may become useful when you're managing big amounts of code and and script files but but you don't have to know about them as far as you're not building big programs so I think this is enough to know for now in the next lecture I'll start writing code right away by explaining the basics of python so talk to you in the next lecture well you should already know that variables in programming are simply some sort of containers where we can sort everything as in other programming languages in Python we can sore numbers text lists file FES data and all kinds of objects it is very easy to create a variable in Python just pick a name for a variable and store something on it I creating a variable here and assigning it a number so potato price equals 3 and yet another value in this other variable amount equals 2.5 notice here that we implicitly declare the data type stored in the variable in many other programming languages you'd have to write something like um int potato price to declare that the variable will be an integer so int stands for integer and after that you store the value inside your variable in Python however you don't have to write that much indeed if the number you are assigning to your variable is a whole number python understands that and makes the variable an integer type but I'll tell you more about data type in the next lectures for now let's check the data type that our variables hold and we can do that using the type function so we're going to print out the type of the data that our variables hold so to do that type print and then Open brackets and inside the brackets we'll write what to print out on the screen so in this case we want to print the variable data type and the data type is generated by the type function so type and then we pass in the value in the type function which in this case is a potato priz variable so python tells us that the value of the potato priz variable is an integer and also let's check the the other variable as well print again type and then we enter the other variable and the value of the other variable is a floating Point number called float for short in and I'll tell you more about data types in the next lectures and a few more stuff now uh you can assign any other values in the existing variables as well even different data types from what the variable currently holds so here I'm going to assign a string to my potato priz variable strings are like text but we'll cover that later so potato price equals fre for today and the variable will have discorded this previous value by keeping the new one functions functions functions there are two types of functions builtin and custom build-in functions are functions that have already been created by python authors and are already use from python programmers which is us the print function is an example of a building function but in this lecture we're going to talk about custom functions and custom functions are super useful I'll refer to custom functions as just functions from now on so a function is an algorithm written by us that computes an output given a certain input the key benefit of function is that you can write a function only once but you can use it as many times as you want by just calling it which is very simple uh here is how to write a function in Python I'm going to create a function here that calculat play the cast of potatoes given the price and the amount so we use the word the keyword def to tell python that we are about to define a function and after that we choose a name for our function I'll name my function uh potato coast once we write the function name we set the input parameters for the function and we can now write what the function will compute and what it return as an output in this case we want to compute the cost of potatoes given the price and the amount so cost equals potato price times amount and we also want let's say to print out the potato type now we we are printing out the potato type but we also want to return the calculated cost when the function is executed later we can either do it using the pr function or we can use a return keyword I'm using the return keyword here and see now how easy is to call the function once we have created it so potato codes and we write the values which are called attributes now uh notice that we are inputting values for each of the parameters in the given order and what we get is the printed potato type and the computed cast you can now execute the function as many times as you want using different values and the last thing to mention here is that we wrote Our function in the IPython console as I have told you before this is a platform for testing if we close the IPython console we will lose our function definition and we will not be able to call it anymore so normally uh we want to sore our function in a script for later use in that case we have to write it in a DOT P script once we do that we can reuse a function in the future so that was how to define and call a function as far as data types are concerned we have so far mentioned integers strings and floats now you're going to learn two other data types that are list and Toes both lists and tobl are often referred to as sequences because they are SE quences of objects let's start with lists lists are the most important between the two so let's start talking about lists list is a sequence of objects and these objects can be numbers strings files and many other data types let's create a list of integers I'm going to call my list file list and add three integers in the list and let's quickly see what we got so it's a list of integers now uh each value of the list is called the list item lists are extensively use when automatically performing multiple actions or iterating if you like if you want to add more items to a list you can use aen method so aen is a list method that adds a new element at the end of the list and we use the dot notation to apply a method to an object now uh lists are indexed meaning that every element of the list every item of the list has a certain index starting from zero so for our list 2015 holds an index of zero 2016 has an index of one and 2017 has an index of two indexes are useful when we want to access certain items of the list for instance if we want the second element we call the element with index one we write the list name and the index of the item we want to call inside square brackets and we get the second item and this item behaves just like an independent object for example in this case we have an integer as you see now you saw that we were able to modify a list and we did that by adding an item at the end of our list some sometimes you don't want your list to be modified for some reason and in such cases we use toles to create a tole just use this syntax so to declare list we use square brackets for toes we use round brackets it is rare to use toles but in case you want your series to be immutable toles are always there for you so you just learn what list and Tes are and more data types in the next lecture as far as data types are concerned we have so far mentioned integers strings and floats now you're going to learn two other data types that are lists and toles both lists and to are often referred to as sequences because they are sequences of objects let's start with lists lists are the most important between the two so let's start talking about list list is a sequence of objects and this object objects can be numbers strings files and many other data types let's create a list of integers I'm going to call my list file list and add three integers in the list and let's quickly see what we got so it's a list of integers now uh each value of the list is called the list item lists are extensively used when automatically performing multiple actions or iterating if you like if you want to add uh more items to a list you can use a pen method so append is list method that adds a new element at the end of a list and we use a DOT notation to apply a method to an object now uh lists are indexed meaning that every element of the list every item of the list has a certain index starting from zero so for our list 2015 holds an index of zero 2016 has an index of one and 2017 has an index of two indexes are useful when we want to access certain items of the list for instance if we want the second element we call the element with index one we write the list name and the index of the item we want to call inside square brackets and we get the second item and this item behaves just like an independent object for example in this case we have an integer as you see now you saw that we were able to modify a list and we did that by adding an item at the end of our list sometimes you don't want your list to be modified for some reason and in such cases we use topples to create a tole just use this syntax so to declare list we use square brackets for toes we use round brackets it is rare to use toles but in case you want your series to be immutable tles are always there for you so you just learn what list and Tes are and more data types in the next lecture in this lecture you will learn about sets and dictionaries remember lists and TOS were referred to as sequences well sets and dictionaries are referred to as collections because they are unordered collections of items let's start explaining sets a set is an another collection of unique items and remember unique items not duplicate items allowed in a set uh we can create a site using curly brackets just like this let's say file set and I'll store three integers in my set a simple and practical use of sets now is when you have a list that has duplicate items and you want to remove those duplicate items from it let's say you have this list file list okay and we have two duplicate items and to make a sequence of unique elements you have to convert it to a set object and we can convert a list to a set object using the set function when you do that duplicates will be removed automatically so we are sort of updating our file this variable with a new value in this line of code uh this new value will be a set that is generated by converting the the list object to a set object so now printing the file list will reveal that duplicate items have been removed and we now have a set object not a list anymore and that is because we converted our list to a set but don't believe me and check the type of the object always so if you want to retain your list data type you can convert the set back to a list using the list function this time so file list equals list and we pass the set object to the list function more data types now dictionaries let's try to explain them by making a comparison with list so in the of lists we were able to access items using their indexes for dictionaries we can access items using index is declared explicitly by us here's the dictionary I'll call my dictionary file dict and we use curly brackets to Define dictionary and then we write the index a column and a corresponding item so don't forget that each item has its own data type so if you use quotes for an item that makes that particular item a string and so on the items in this case are 2015 2017 and 2019 and they are referred to as values so remember values when we talking about dictionaries and the indexes are last year this year and next year and they are referred to as keys so what we are dealing here is an object constructed by pairs of keys and Val now in the case of list and tops we were able to access items using the default indexes in the case of dictionaries you can access the dictionary values using their corresponding keys and that will return the value attached to the year key remember that once we opened a file we had to close it later using the close method well in this lecture you're going to learn a more solid way that closes a file for you once it has finished working with it and the solid method is called width so you will learn the WID method in this lecture before we did this to open a file we created a variable and then we use the open method to open a file and then we use the write method to write something in that file and later on we had to close that file what you you want to do instead is write a width statement so to write a width statement follow this syntax start with a with keyword and then we write the open method the file path the writing method and then the variable the next line then is used to write the actions that we want to perform on the open file in this case we would like to write a line for example so don't forget to indent the second line again we use indentation for the WID method and so how do we read this statement well just like this with the open test induct txts file we perform the actions in the next line uh the benefit here is that the with method will close the file for us once the the action below it have been completed so it's a very comp method that is highly recommended so what you're looking at is a script you wrote in the previous exercise and what you basically did there is that you asked you asked the user to enter some input so the user enter a longitude and a Latitude value and then you pass these values uh to the new Point method uh in this lecture I'll show you how to actually generate a KL file out of a CSV file uh this is a more efficient way compared to the previous method so compared to the existing script you're looking at now uh because using a CSV file you can actually pass many many longitude and latitude values at the same time and get a KL file generated so now you have to think how do we get the data out of the CSV file well I think I already taught you that you can use the panas library to do just that panas is powerful data analysis library and it can efficiently read CSV data and manipulate them so I'm going to delete these two lines here okay and import the panas library great uh now the C file I'm talking about is this one here so we have two columns and four rows and I'm going to Kip my file here and my spider here good so what we want to do now is is create a data frame object and we use a CSV method for that and here we pass in the path of the CSV file so now we we already have the data of the CSV file inside Python and we keeping them in the data frame object what we want to do now is create a for Loop which will iterate through all these four rows and then it will execute the new Point method four times so the new Point method we'll get the longitude and latitude values for each of these rows so the idea is that we have to start the loop above the new Point method so let's say four loan let in okay so so far I taught you how to iterate with one variable but not with two variables at the same time so you used to iterate with one variable through a single list here to iterate with two variables in two lists we have to use a zip function so the zip function allows you to iterate through two Leist at the same time and now our lists are the first lease will is going to be the longitude column so to access such a Leist we we call the data frame and then in the square brackets we write the column name of the data frame which is longitude and then we're passing the second list which is latitude great that's the idea uh now you want to indent this line here and we don't have any name column in our CSV so I'm going to delete this and then the arguments that we pass here to the course parameter have to reflect the names of variables here so I'm going to pass loan and let and that's it uh we have something here it says invalid syntax of course we have an added the colum here and that's it and we don't want to iterate through the save method because the idea here is that we will create Four Points using the new Point method and then once these points have been added to the object then we just save this object to a caml file great let's run now and we have an error so the error has to do with a long tud uh string and of course passage for the wrong name because the correct name is longitude great let's execute again now and let's check the KML file so now we should expect Four Points in the KL file and that's how it is so in this uh lecture we leveraged the the CSV data to create a KML file and you may never have to create KML files in your life but you may have to process CSV files and the pandas library is a great library for that and here you saw how to efficiently iterate through the rows of a CSV file so hope you learn something from this lecture and see you in the next lecture all right we have this Python program which if executed say Python and script name we get this graphical user interface which works great great and does the work the problem is that if you want to give this program to someone else who don't have python skills or or they don't even have python installed in their computer they wouldn't be able to execute your script and get the KML file at the end so what you can do in this case is produce an executable file and that would be a XF file on Windows and app if you are on a Mac then you can just give that that exit file to someone and they can execute it and get the results so to make such a program such an executable file you'd want to use a python Library called Pi installer to install the library you use pip all right my P installer was already installed there so I can just go ahead and use it now notice that I am in uh the C temp directory which is where my file is located and now I can just call P iner and then the tab to get the script name note that we are in the command line here in the terminal so I have an open Python and if we leave this expression as it is now uh we would actually get a bunch of files and among them would be thexa file this method is good that uh in that if uh some problem happens you would be more able to actually troubleshoot the problem and and go to the specific file that caused the problem and then maybe solve the problem but if you want a single file a single. xit file or a single. app file for Mac You' want to add a parameter here called one file and there's yet another parameter you would want to add and that's the window parameter the window parameter will create a single window for your uh program so without a command prompt on the on the background and that's it you execute this and You' have to wait a while until the process finishes and that was apparently successful but let's check your executable file should be inside the this folder and here it is so it's the same program and does the same thing if you want to give this program to someone you can just send the XA file and they will be able to execute it without needing python installed and that wraps up uh this section hope you enjoy that thank you