Crystal Clear Explanation of Python List Comprehensions

A highly intuitive way for understanding them .Crystal Clear Explanation of Python List Comprehensions

List comprehension is a way of creating lists based on other iterables such as sets, tuples, other lists, and so on. It can also be described as representing for and if loops with a simpler and more appealing syntax. List comprehensions are relatively faster than for loops though.

The basic structure of a list comprehension is as follows.

(image by author)

It seems quite simple but might get tricky in some cases. In this article, we will start from a very simple list comprehension and steadily increase the complexity. I will clearly explain how to represent and understand highly complex list comprehensions as well.

List comprehensions are preferred over for and if loops in most cases because

• They are relatively faster than for loops.
• They are considered to be more pythonic than for loop and map function.
• The syntax of list comprehension is easier to read and understand.

Let’s start with a simple example.

words = ['data','science','machine','learning']

We want to create a list that contains of the length of each word in the words list. Let’s perform the task using both a for loop and list comprehension.

#for loop
a = []
for word in words:
   a.append(len(word))
#list comprehension
b = [len(word) for word in words]
print(f"a is {a}")
print(f"b is {b}")
a is [4, 7, 7, 8]
b is [4, 7, 7, 8]

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