Python: why is zip(*) used instead of unzip()? [closed]

Question

Given the zen of python why is zip(*) used to unzip instead of some function named unzip()? For example Transpose/Unzip Function (inverse of zip)? shows how to unzip a list.

>>> zip(*[('a', 1), ('b', 2), ('c', 3), ('d', 4)])
[('a', 'b', 'c', 'd'), (1, 2, 3, 4)]

How is that more:

• Beautiful than ugly
• Explicit than implicit
• Simple than complex
• Readable
• etc.

then

>>> unzip([('a', 1), ('b', 2), ('c', 3), ('d', 4)])

?

What am I missing here?

Answer 1

You're not actually unzipping when you do zip(*your_list). You're still zipping.

zip is a function that can take as many arguments as you want. In your case, you essentially have four different sequences that you want to zip: ('a', 1), ('b', 2), ('c', 3) and ('d', 4). Thus, you want to call zip like this:

>>> zip(('a', 1), ('b', 2), ('c', 3), ('d', 4))
[('a', 'b', 'c', 'd'), (1, 2, 3, 4)]

But your sequences aren't in separate variables, you just have a list which contains them all. This is where the * operator comes in. This operator unpacks the list in a way that each element of your list becomes an argument to the function.

This means that when you do this:

your_list = [('a', 1), ('b', 2), ('c', 3), ('d', 4)]
zip(*your_list)

Python calls zip which each element of your list as an argument, like this:

zip(('a', 1), ('b', 2), ('c', 3), ('d', 4))

This is why an unzip function isn't necessary: Unzipping is just another kind of zip, and is easily achievable with just the zip function and the * operator.