Conditional statements

We are now heading into the sections where we learn how a computer makes its decisions.

"Oye, python, wake up"

"What are you so hyped up about in the early morning, Tikles. I didn't even have my morning electro-coffee yet"

"(Tickles smirk) You wanna learn how to communicate with humans"

"What are you, a kid? *facepalm I'm not so enthusiastic as you"

"Cmon man, here's your 800 watt coffee"

"Ohh, yeahhhhh. What do you want me to do, Sir Tickles"

Code Blocks

So far, we've studied data types, variables and some operations like assignment, comparison. All of those topics didn't require the knowledge of indentation or code blocks. But from here onwards, it'll become critical to understand what exactly a code block is.

We have used whitespace and code lines as how we liked till now. It was because the functions and operations we have used so far were part of just one code block.

Lets take an example to understand this.

When we run $$a=10$$ this whole statement is complete which means its a complete code block of one statement. There might be other code chunks which uses the variable a, but those other code chunks are part of different code block.

In here, $$a=10$$ and $$print(a)$$ have different code block but they have same indentation.

Lets look a more challenging example

If statement

if statements are used to execute a certain code block depending on a condition. The condition could be True or False.

Notice the indentation of the print statement.

The print("Code is executed") is indented under the if code block

We usually use 4 whitespaces as indentation for better code readability.

The whole syntax goes

Lets use a False boolean condition. It'll not be executed as the condition is set to false.

Lets look at a more practical example of why we use booleans as conditions.

Remember, the comparison operators output a boolean value. We use this boolean value as a condition.

Here, $$a = 10$$ $$b = 11$$ and the if statement had same indentation from the left.

But the print statement was written inside the if code block, so the print statement needs to be indented 4 whitespaces, to make the print a part of if statement

Here, we use two if code blocks, which have their own print statements indented.

The two if statements here are mutually exclusive so they share the same indentation. One if does not depend on other if statement here.

There are three if statements now. But of course only the first two if statements are executed because of the condition True.

Now, let's talk about else block. Things will become clear as we practice on these topics.

if else block

Here we will first use True condition. Python reads it as

if the condition is True, do something.

In the following code, we have written, if the condition is true, print("We are inside if block"),

otherwise print("We are inside else block")

In one if-else condition, either the if or the else gets executed.

As you've seen, either the if statement gets executed at once or the else statement gets executed.

Lets experiment with variable values

Because now a is 1 and b is 5, and that makes a>b False, so now the else block will run.

Lets make both a and b equal

elif statement

Its something along the lines of "else if".

If in the previous example we wanted to use multiple condition checks to get an output of

a is equal to b

In python we write this else if statement as elif

In the previous statement, if elif and else share the same indentation but only one of them will be executed.