Loop vs Comprehension

Hi Pythonistas!

Today we are going to compare the speed difference between a loop and list comprehension. Let's consider the example. 

Code

import timeit

def using_loop():
    numbers = list(range(50))
    double = []
    for number in numbers:
        double.append(number * 2)
    return double

def using_comprehension():
    numbers = list(range(50))
    return [number * 2 for number in numbers ]

time_taken = timeit.timeit(using_loop, number=1000_000)
print("Time taken for using_loop", time_taken)

time_taken = timeit.timeit(using_comprehension, number=1000_000)
print("Time taken for using_comprehension", time_taken)

Output

Time taken for using_loop 2.5781862180001553

Time taken for using_comprehension 1.8577961320002032

Why:

 

If we look into the internals of both the code append method makes the code slower. But for list comprehension python is internally called a bytecode called LIST_APPEND. This make the comprehension more faster than the loop. Another thing is it make the code more pythonic also

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