Is it ever a good idea to enumerate a python range so you get the index twice?

Question

Sorry for the weird title but I couldn't think of a better way to explain it. I saw someone do this once and didn't think it was a good idea but I wanted to check. Basically, he wanted to return the numbers 0-3 and do two different things with them. Say he wanted to use one as a key to a dictionary and the other in a value calculation, like this:

d{0:0, 1:1, 2:4, 3:9}

So he did this to return the index twice:

d = {}
for i, v in enumerate(range(4)):
    d[i] = v**2

Is that better than writing d[i] = i**2? I thought it was weird to enumerate range(4). I know this might be somewhat subjective but is this bad design or just a preference thing? What's the best practice?

Answer 1

This is not great design. For starters it would be less efficient to enumerate the range.

The code you provided would produce the same result as this:

d = {}
for i in range(4):
    d[i] = i ** 2

I would recommend trying variations out in the python console. The advantage your code has over this is that it sets up i and v so if you did want to modify either of these in different ways it could make it clear, especially for maths students (I have seen a whole host of unpythonic things which they do)