Conditional programming

Conditional programming, or branching, is something you do every day, every moment. It's about evaluating conditions: if the light is green, then I can cross; if it's raining, then I'm taking the umbrella; and if I'm late for work, then I'll call my manager.

The main tool is the if statement, which comes in different forms and colors, but basically it evaluates an expression and, based on the result, chooses which part of the code to execute. As usual, let's look at an example:

# conditional.1.py
late = True 
if late: 
    print('I need to call my manager!') 

This is possibly the simplest example: when fed to the if statement, late acts as a conditional expression, which is evaluated in a Boolean context (exactly like if we were calling bool(late)). If the result of the evaluation is True, then we enter the body of the code immediately after the if statement. Notice that the print instruction is indented: this means it belongs to a scope defined by the if clause. Execution...