(func(a) for a in collection)
map(func, collection)
as equivalent. If you want a list (and not a generator), you would need to do this:
[func(a) for a in collection]
list(map(func, collection))
For me, the first set (comprehensions) of notation has a more mathematical feel to it, i.e. { x^2 | x \in 0...10 }. Just replace the bar with "for" and it's almost the same thing.
I believe the documentation for `filter` even mentions that it is equivalent to the comprehension[1].
> It may just be a matter of which a person learned first.
I think this is the case, for me map is much harder to read. But I also think that comprehensions go back to math sets, so I was familiar with this even before learning any programming. Therefore comprehensions clicked immediately for me and it's by far my favourite python feature.
I learned both around the same time, but even in good functional languages like Haskell, using a comprehension for anything more than simple problems results in an unreadable mess.
map or filter are much easier to read for complex data manipulations and as a bonus, their composition rules make it easy to increase performance. For example, if you see two map functions together, you can wrap them in a compose and only map over your elements once. This isn't as immediately obvious when you're using comprehensions.
> [ manager.name for manager in set([
person.manager for person in employees
])]
?
I assume with something like set() or unique() you need to create the intermediate iterable anyway, but without it I have trouble finding an example where doing a single list comprehension wouldn't suffice.
I believe the documentation for `filter` even mentions that it is equivalent to the comprehension[1].
[1] https://docs.python.org/3/library/functions.html#filter