Condition Statements

Condition statements or Control flow statements or Desicion Control Statements are statements that are used to control the flow or execution of a program. The flow is controlled the values of few variables that decide the proceedings of a program.

The conditions statements have same basic structure in all programming languages. The list of Control statements are: 1. if statement 2. if - else statements 3. if - elif - else statements 4. Nested if - else statements 5. Inline if - else statements

The condition given in the if statements need to result in allowed boolean values.
1. For integral type: value!=0 is True and value=0 is False
2. For list and tuple: length(value)>0 is True and length=0 is False
(boolean as applicable)

1. if statement:

Executes the statements inside the block only if the condition is satisfied.

Syntax:

if condition:  
    Statements

Note: Indentation in python indicates blocks.

IN [2]

# Example
x = 14
y = 18
if y>x:
    print(y)

stdout

18

IN [1]

# Example2
x = int(input())
if x:
    print('not zero')

# Input: -1

stdout

-1
not zero

2. if - else statements:

Executes else when if condition fails
Syntax:

if condition1:  
    Statements  
else:  
    Statements

3. if - elif - else statements:

Checks for truth of elif statement when if statement fails. Chain of if-else
Syntax:

if condition1:  
    Statements  
elif condition2:  
    Statements  
else:  
    Statements

4. Nested if - else statements:

if else within another if else statement

Syntax:

if condition1:  
    if condition2:  
        Statements  
    else:  
        Statements  
else:  
    if condition3:  
        Statements  
    else:  
        Statements  

5. Inline if - else statements:

One liner of if else statements

Syntax:

Statement1 if condition else Statement2