When is range(len(a)) preferred in Python?

General Discussions
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1

Are there real-world use cases for range(len(a)) in Python?

Often in Python questions, we see patterns like this:

for i in range(len(a)):
    print(a[i])

This can be replaced with a simpler version like:

for e in a:
    print(e)

Similarly, when modifying elements:

for i in range(len(a)):
    a[i] = a[i] * 2

This could be written as:

for i, e in enumerate(a):
    a[i] = e * 2

Or even:

a = [e * 2 for e in a]

For filtering over indices:

for i in range(len(a)):
    if i % 2 == 1: continue
    print(a[i])

Could become:

for e in a[::2]:
    print(e)

Finally, when only the length of the list is needed, such as:

for _ in range(len(a)):
    doSomethingUnrelatedToA()

You might use:

for _ in a:
    doSomethingUnrelatedToA()

Given Python’s rich constructs like enumerate, slicing, and comprehensions, is there any situation where range(len(a)) is still necessary or preferred? How does it hold relevance in practical cases when working with range len Python?

2

So, from my experience with Python, when you’re working with modifying a list in place, range(len(a)) comes in super handy. It allows you to access each element by its index and update them directly. It’s especially useful when you’re doubling values or making other modifications across the list. Here’s an example:

for i in range(len(a)):
    a[i] = a[i] * 2
3

Great point, @Rashmihasija. Building on that, I’ve found range(len(a)) also works really well when you need to iterate over multiple lists simultaneously. If you have two or more lists of the same length and want to perform actions on both at the same index, this becomes your go-to. You can loop through their indices and print or process their corresponding elements. Here’s an example to illustrate:

for i in range(len(a)):
    print(a[i], b[i])
4

Absolutely, @akanshasrivastava.1121! That’s a perfect use case. Adding to that, I’ve also used range(len(a)) when I need to apply specific conditions based on indices. For instance, if you want to print elements only at even indices, range len python is a simple and effective tool. You can check for even numbers in the index and then apply your logic, like so:"

for i in range(len(a)):
    if i % 2 == 0:
        print(a[i])