Python Coding challenge - Day 601| What is the output of the following Python Code?

 

Code Explanation:

1. Importing takewhile from itertools

from itertools import takewhile

itertools is a standard Python module that provides fast, memory-efficient tools for working with iterators.

takewhile(predicate, iterable) is a function that returns elements from the iterable as long as the predicate is true. Once the predicate returns False, it stops — even if there are more elements left.

2. Defining a Generator Function letters

def letters():

    for ch in "abcdefg":

        yield ch

This is a generator function.

It loops through the string "abcdefg" and uses yield to lazily produce one character at a time (i.e., an iterator over 'a', 'b', ..., 'g').

Using yield makes this function a generator, meaning it doesn’t return all items at once — instead, items are produced one at a time when requested.

3. Using takewhile to Filter Items

result = list(takewhile(lambda x: x != 'e', letters()))

letters() is called, returning a generator that yields 'a' through 'g'.

takewhile(lambda x: x != 'e', ...) processes these letters:

It keeps yielding characters as long as x != 'e' is True.

The moment it encounters 'e', it stops, even though there are more characters ('f', 'g') in the generator.

Wrapping the result in list() collects all the values into a list.

4. Printing the Result

print(result)

This prints the final list returned by takewhile.

Final Output

The generator yields: 'a', 'b', 'c', 'd', 'e', 'f', 'g'

takewhile(lambda x: x != 'e', ...) stops before 'e', so the result is:

['a', 'b', 'c', 'd']

Download Book - 500 Days Python Coding Challenges with Explanation