Using if, for, and while Loops in Python

Definition and Explanation

• if statement: Used for conditional execution. It runs a block of code only if a specified condition is true.
• for loop: Used for iterating over a sequence (like a list, tuple, or range).
• while loop: Repeats a block of code as long as a condition remains true.

Syntax Overview

• If statement:

``python
if condition:

code block

elif another_condition:

another block

else:

else block

`

• For loop:

`python
for variable in sequence:

code block

`

• While loop:

`python
while condition:

code block

`

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Worked Example

Problem: Print all even numbers from 1 to 10 and state whether each is greater than 5.

`python
for i in range(1, 11):
if i % 2 == 0:
print(i, "is even", end="; ")
if i > 5:
print("greater than 5")
else:
print("not greater than 5")
`

Step-by-step explanation:

1. for i in range(1, 11):

Loops through numbers $1$ \to $10$. 2. `if i % 2 == 0:` Checks if $i$ is even (since $i mod 2 = 0$). 3. If even, prints the number and checks if $i > 5$. 4. Prints whether the number is greater than $5$ or not.

Sample Output:
`
2 is even; not greater than 5
4 is even; not greater than 5
6 is even; greater than 5
8 is even; greater than 5
10 is even; greater than 5
`

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Takeaways

• Use if for conditional logic, for for iterating over sequences, and while` for repeating code with a condition.
• Combine these constructs for more complex logic and control flow.
• Understanding their syntax and use cases is fundamental for Python programming.