Python Interview Questions & Answers: for loop

Following are some sample interview questions and answers related to Python for-loops. These questions and answers aim to test understanding of basic to intermediate for loop concepts in Python.

Q1: What is a for loop in Python?

A1: A for-loop in Python is a control flow statement that iterates over a sequence (like a list, tuple, dictionary, or string). It executes a block of code for each item in the sequence.

for item in [1, 2, 3]:
    print(item)

Q2: How do you iterate through a list using a for loop in Python?

A2: To iterate through a list in Python, you can use the for keyword followed by a user-defined variable name, the in keyword, and the list you want to iterate over. Here’s an example:

my_list = [1, 2, 3]
for item in my_list:
    print(item)

Q3: How can you loop through a string character by character in Python?

A3: You can loop through a string character by character using a for-loop, similar to iterating through a list.

for char in "Hello":
    print(char)

Q4: How do you use the range() function in a for loop?

A4: The range() function generates a sequence of numbers over which you can iterate using a for-loop. For example, to print numbers 0 to 4:

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

Q5: What is the purpose of the break statement in a for loop?

A5: The break statement is used to exit the for-loop before it has gone through all the items in the sequence. It’s useful when you want to terminate the loop based on a certain condition.

for i in range(10):
    if i == 5:
        break
    print(i)

Q6: What is a nested for loop? Provide an example.

A6: A nested for-loop is a for-loop within another for-loop. It allows you to iterate over multiple sequences, often used for 2D arrays or lists of lists.

for i in range(3):
    for j in range(2):
        print(f"(i, j) = ({i}, {j})")