How to use filter, map, and reduce in Python 3

Question

filter, map, and reduce work perfectly in Python 2. Here is an example:

>>> def f(x):
        return x % 2 !=         


        

Answer 1

You can read about the changes in What's New In Python 3.0. You should read it thoroughly when you move from 2.x to 3.x since a lot has been changed.

The whole answer here are quotes from the documentation.

Views And Iterators Instead Of Lists

Some well-known APIs no longer return lists:

• [...]
• map() and filter() return iterators. If you really need a list, a quick fix is e.g. list(map(...)), but a better fix is often to use a list comprehension (especially when the original code uses lambda), or rewriting the code so it doesn’t need a list at all. Particularly tricky is map() invoked for the side effects of the function; the correct transformation is to use a regular for loop (since creating a list would just be wasteful).
• [...]

Builtins

• [...]
• Removed reduce(). Use functools.reduce() if you really need it; however, 99 percent of the time an explicit for loop is more readable.
• [...]