5 tips for writing loops more efficiently in Python

Mondo Technology Updated on 2024-01-30

If possible, try to avoid loops and use built-in function methods instead. For example, when we calculate the sum of the list elements, we can use sum(). 

Use loops to sum the list. 


numbers = [1, 2, 3, 4, 5, 6]


result = 0


for num in numbers:


result += num


print(result) 


Use sum() to sum the list. 


result = sum(numbers)


print(result)
When you need to iterate over a list, and you need to use both indexes and elements, use the built-in function instead: enumerate(). 

Use range().


data = ["a", "b", "c"]


for i in range(len(data)):


print(i, data[i])


Use enumerate().


for idx, val in enumerate(data):


print(idx, val)
When traversing multiple lists, use zip(), which returns a tuple iterator. 

Use range().


a = [1, 2, 3]


b = ["a", "b", "c"]


for i in range(len(a)):


print(a[i], b[i])


Use zip().


for val1, val2 in zip(a, b):


print(val1, val2)
Use list inferences or generator expressions to simplify, make them appear more concise, and run faster. 

lst = 


for i in range(1, 10):


if i % 2 == 0:


lst.append(i**2)


print(lst)


Use list inferences. 


lst = [ i**2 for i in range(1, 10) if i % 2 == 0]


print(lst)


fruit = [("apple", 5), "banana", 10), "apple", 20)]


sum1 = 0


for i in fruit:


if i[0] == "apple":


sum1 += i[1]


print(sum1)


Use generator expressions. 


sum_item = (i[1] for i in fruit if i[0] == "apple")


sum1 = sum(sum_item)


print(sum1)
The IterTools module provides functions for creating iterators for efficient loops. Let's take a look at three of these functions: islice(), pairwise(), takewhile().

Creates an iterator that returns the specified element from the iterable object. 

lst = ["1", "2", "3", "4", "5", "6"]


for i, j in enumerate(lst):


if i >= 3:


breakprint(j)


from itertools import islice


lst2 = islice(lst, 3)


for i in lst2 :


print(i)
A pair of samples is returned at a time. 

from itertools import pairwise


data = 'abcde'


for i in range(len(data)-1):


print(data[i], data[i+1])


for pair in pairwise('abcde'):


print(pair[0], pair[1])
Iterable objects are retrieved and included in the generator object when the current item satisfies the criteria. 

for item in [1, 2, 4, -1, 4, 1]:


if item >= 0:


print(item)


else:break


from itertools import takewhile


items = takewhile(lambda x: x >= 0, [1, 2, 4, -1, 4, 1])


for item in items:


print(item)
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