Which PEP (design document) decides about using map(function,iterable) instead of implementing list.map()

Question

I was wondering the reason why there is no list.map() in the Python standard library.

There are alternatives, like map(function,iterable), and list comprehensions.

I cannot find the PEP (design document) that explains the whys of choosing map instead of implementing list.map()

Suppose we have a list like this:

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

I believe this code:

foo.map(function)

# or

foo.map(lambda x: x*2)

Is more readable than:

least_readable = list(map(lambda x: x*2, foo))

least_readable = list(map(multiply_by_two, foo))

This looks readably enough for me

it_readable_enough_for_me = [multiply_by_two(x) for x in foo]

This looks more readable to me but doesn't exist:

does_not_exist = foo.map(multiply_by_two)

I believe that if that does not exist, there must be a reason for it.

Not just because map(function,iterable) is more general. I guess there must be an important reason behind that I don't see.

Answer 1

None.

PEP 201, the 2nd ever stable implemented PEP, says:

This behavior can already be accomplished in Python through the use of the map() built- in function

The map function is defined in bltinmodule.c, added in commit a6c603. The previous location is itertoolsmodule.c, which was originally introduced in commit 96ef81 on 1st Feb 2003. There are no PEPs adding this feature up until that date.

According to Wikipedia:

Python reached version 1.0 in January 1994. The major new features included in this release were the functional programming tools lambda, map, filter and reduce. Van Rossum stated that "Python acquired lambda, reduce(), filter() and map(), courtesy of a Lisp hacker who missed them and submitted working patches".