`for` Loop in Python [ English ]

Languages

• English

1. Introduction

The for loop in Python is used to repeat a block of code multiple times. When used with the range() function, it is especially useful for numeric iteration.

This approach is commonly used when:

• The number of iterations is known
• You want to work with numbers or indexes

2. Syntax

for variable in range(start, stop, step): # code block

3. Understanding range()

The range() function generates a sequence of numbers.

Forms of range():

1. range(stop)
2. range(start, stop)
3. range(start, stop, step)

4. Basic Example

for i in range(5): print(i)

Output

01234

Explanation

• Starts from 0 by default
• Stops before 5

5. Example with Start and Stop

for i in range(1, 6): print(i)

Output

12345

6. Example with Step Value

for i in range(1, 10, 2): print(i)

Output

13579

Explanation

• Increments by 2 each time

7. Reverse Looping

for i in range(5, 0, -1): print(i)

Output

54321

Explanation

• Starts from 5
• Decreases by 1
• Stops before 0

8. Loop for Table Example

num = 5 for i in range(1, 11): print(num * i)

9. Sum of Numbers

total = 0 for i in range(1, 6): total += i print("Sum =", total)

Output

Sum = 15

10. Nested for Loop with range()

for i in range(1, 4): for j in range(1, 4): print(i, j)

11. Important Points

• range() does not include the stop value
• Default start value is 0
• Default step value is 1
• Negative step is used for reverse looping

12. Summary

• for loop with range() is used for numeric iteration

• range() generates a sequence of numbers

• Forms:

  • range(stop)
  • range(start, stop)
  • range(start, stop, step)

• Supports:

  • forward looping
  • reverse looping
  • nested loops