Why Doesn\'t Modifying a For Loop\'s Iteration Variable Work as Expected in Python, and How Can It Be Fixed?

Rethinking Iteration Variable Modification in Python

When iterating through a sequence using Python's for loop, one may encounter unexpected behavior if attempting to modify the iteration variable. Consider the following Python code:

for i in range(0, 10):
    if i == 5:
        i += 3
    print(i)

The expected output:

0
1
2
3
4
8
9

However, the actual output differs:

0
1
2
3
4
8
6
7
8
9

Why does the value of 'i' not change within the loop, and what can be done to rectify it?

The reason lies in how for loops operate in Python. Each loop iteration involves creating a new scope and assigning a new value to the iteration variable. Modifying the iteration variable within the loop only affects its value within the current iteration, leaving subsequent iterations unaffected.

To achieve the intended behavior, one can utilize a while loop instead. Here's the corrected code:

i = 0
while i < 10:
    # Perform operations and modify 'i' as needed
    if i == 5:
        i += 3

    print(i)

    # Increment 'i' manually within the loop
    i += 1

This approach creates a single scope and allows modifications to 'i' to persist throughout the loop's execution.

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