Sunday, 28 May 2017

Beginners Python Programming Tutorial - How to become a Python Jedi - Part 5 : If-Else statement


Welcome back friends to another post on TheCodingProject and we are back with the fourth chapter of the Beginner Python programming tutorial - How to become a python Jedi. This time we are going to learn about decision making in python using the If-Else statement.

The If-Else statement?
In Python Programming, decision making is done by using a conditional statement like the If-Else statement. An If statement consists of 3 parts →
  • If keyword
  • a conditional operator
  • the values which needs comparison

Now it should be kept in mind that the only values that an If condition returns are a True or a False , Using this True or a False we can decide if the condition that we are trying check is right or wrong.
When Coding knowledge came to my rescue→
Let me tell you a story about how coding knowledge came to rescue . I have this neighbour named Alex who doesn't quite seem to be a regular guy. Wait ! actually he never seemed to me as a regular human 😟. This one day I was visiting him at his home for some work when I noticed something unusual. His living room is decorated with his family photographs, he has the photographs of his entire family tree over there starting from his great grandfather down to him. The weird thing that I noticed was that all the men in these photographs looked similar to him as if he himself was present throughout his family history. Is Alex a Vampire ? 😓 With this frightening thought in mind I ran back to my house and jumped straight to the computer and started to code. Using my superhuman brain I made a python program which would hack into his personal computer and collect all his personal information and then the program would calculate his age & use that knowledge to decide if Alex was really a Vampire. Now, that program is highly confidential so I won’t show you my entire code but as you guys are so much interested I will show you the snippet that is really pivotal in deciding Alex’s truth →





Copy & paste the above code in your editor and run this code. In the above code we have an If condition & an else condition. Let’s assume we have the age as 100. Now when the above code runs the code touches the If condition & checks if age is greater than or equal to 0 or age is less than or equal to 99. Notice that we have used an or operator so the condition becomes True even if only one of the condition matches & as age is 100 ( greater than 0) so the If condition returns a True & the control enters the If statement to print the statement inside the print method.

Let’s modify our If-Else statement to make it more robust. Copy and paste the below code in your editor and give it a spin→







As you can see this time we have an and operator instead of an or. So this time our If condition will return True  only when age is greater than or equal to 0 and less than or equal to 99. Now as we have the value of age out of the bounds of 0 to 99 so the control skips the If condition & jumps to the line of code immediately after that which is the Elif  statement. This kind of expression is known as a  Nested if-else statement, wherein we have another If condition immediately after the first If condition to put a second conditional check and in python programming language it’s written as Elif. In our case the control checks that age is not satisfying even the condition inside the nested If statement so it skips that too and jumps to the next condition i.e the Else  statement and as there are no further condition defined for this else statement, so it returns a True & the statement inside the print method is printed.


Conclusion→
You can define n number of rules using the nested if-else conditional statements. Go ahead & try to extend on the above example code by implementing your own rules with nested if-else statements. The code examples can be found in the Python Decision Making.py file in my Github repo.

So, folks this was all for this week but we shall return with another chapter of this tutorial with some new concepts to learn.

Subscribe to my youtube channel to watch the coding in this tutorial in action.

If you have any questions, suggestions or comments you can post your comment here or you can also bug me on Quora, Twitter or on Facebook.

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