Conditions

Introduction

Conditions are essential instructions in programming. They allow controlling the execution flow of a program based on certain conditions.

In Python, conditional structures allow performing tests and executing different parts of code based on the results of these tests.

Comparison and logical operators

Conditions in Python use comparison operators and logical operators to evaluate expressions.

Comparison operators

== : equal to
!= : not equal to
< : less than
> : greater than
<= : less than or equal to
>= : greater than or equal to

Logical operators

and : logical and
or : logical or
not : logical not

Conditional structure `if`

The basic structure for conditions in Python is the if instruction.

x = 10
if x > 5:
    print("x is greater than 5")

Conditional structure `if...else`

The else instruction allows defining a block of code that executes when the if condition is false.

x = 3
if x > 5:
    print("x is greater than 5")
else:
    print("x is less than or equal to 5")

Conditional structure `if...elif...else`

The elif instruction (contraction of "else if") allows testing multiple conditions in sequence.

x = 8
if x > 10:
    print("x is greater than 10")
elif x > 5:
    print("x is greater than 5 but less than or equal to 10")
else:
    print("x is less than or equal to 5")

Nested conditions

Conditions can be nested to verify multiple conditions.

x = 7
y = 5
if x > 5:
    if y > 3:
        print("x is greater than 5 and y is greater than 3")
    else:
        print("x is greater than 5 but y is not greater than 3")

Using complex conditions

The and, or, and not operators allow combining multiple conditions.

x = 4
y = 6
if x > 2 and y < 10:
    print("x is greater than 2 AND y is less than 10")
if not(x > 5 or y > 10):
    print("x is NOT greater than 5 OR y is NOT greater than 10")

Best practices

Clarity: Avoid overly complex conditions. Use intermediate variables to clarify your code's intention.
Testing: Always test your conditions with different sets of values to ensure they work correctly.