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What is the difference between "for" and "while" loop in Python?

In Python, both for and while loops are used for iteration and repetition, but they have some key differences:

Syntax:

  • for loop: The for loop is used for iterating over a sequence (such as a list, tuple, string, or range) or any iterable object. It iterates over each element of the sequence one by one until the sequence is exhausted.
  • while loop: The while loop is used for executing a block of code repeatedly as long as a given condition is true. It continues to execute the loop as long as the condition remains true.

Initialization:

  • for loop: The for loop automatically initializes an internal counter or iterator variable and sets it to the first element of the sequence. It doesn't require explicit initialization.
  • while loop: The while loop requires explicit initialization of loop control variables before the loop starts. You need to initialize the variables before the loop and update them inside the loop body.

Termination Condition:

  • for loop: The for loop iterates over each element of a sequence until it reaches the end of the sequence. The loop terminates automatically when all elements have been processed.
  • while loop: The while loop continues executing as long as a given condition remains true. It relies on the condition being explicitly evaluated at the beginning of each iteration. You need to ensure that the condition eventually becomes false to avoid an infinite loop.

Use Cases:

  • for loop: The for loop is commonly used when you have a known sequence or iterable object and want to iterate over its elements. It is suitable for situations where you need to perform a specific operation on each element in a sequence.
  • while loop: The while loop is useful when you need to repeat a block of code until a specific condition is met. It is suitable for situations where the number of iterations is not known in advance or when the termination condition is based on a specific condition being satisfied.

Here's an example to illustrate the difference between for and while loops:

# Example with for loop
numbers = [1, 2, 3, 4, 5]
for num in numbers:
    print(num)

# Example with while loop
count = 1
while count <= 5:
    print(count)
    count += 1

In the first example, a for loop is used to iterate over the elements of the numbers list. Each element is assigned to the variable num, and the loop body is executed for each element. The output is:

1
2
3
4
5

In the second example, a while loop is used to repeatedly print the value of count as long as it is less than or equal to 5. The loop starts with an initial value of count set to 1, and the loop body is executed until count becomes 6. The output is:

1
2
3
4
5

To summarize, for loops are used for known sequences or iterable objects, iterating over each element until the sequence is exhausted. while loops are used for repeating a block of code based on a condition that is explicitly evaluated at the beginning of each iteration. Choose between for and while loops based on your specific use case and the nature of the iteration or repetition you need to perform.

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