How to Get map() to Return a List in Python 3.x

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Recap: Python’s map() function takes a function and an iterable—such as a list—as arguments. It then applies the function to each element in the iterable.

It returns a map object. ?

But what if you don’t need a map object but a list?

Old: In Python 2.x this was easy: the map() function simply returned a list rather than an iterable map object. 

# Python 2.X
print(map(lambda x: x+1, [1, 2, 3]))
# Output: [2, 3, 4]

New: But if we try this in Python 3.x, the output is not as pretty:

print(map(lambda x: x+1, [1, 2, 3]))
# Output: <map object at 0x0000013CE75DB4E0>

Bah!

Let’s fix this!

Solution: list(map(...))

To get Python’s built-in map() function to return a list in Python 3.x, pass the map object into the list() constructor to convert the iterable map object into a list. For example, to convert the map object created by map(lambda x: x+1, [1, 2, 3]) to a Python list, use list(map(lambda x: x+1, [1, 2, 3])). 

print(list(map(lambda x: x+1, [1, 2, 3])))
# Output: [2, 3, 4]

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