How to get a map() to return a list in Python 3.x?

In Python 3.x, the built-in map() function returns an iterator instead of a list. This design choice conserves memory by not creating an entire list in one go. However, if you need a list, simply wrap your map() call with the list() constructor:

def square(x):
    return x * x

nums = [1, 2, 3, 4]
squared_list = list(map(square, nums))
print(squared_list)
# Output: [1, 4, 9, 16]

1. Iterator by Default:

In Python 2, map() returned a list. In Python 3, it returns a “map object,” which is an iterator.

2. Convert to List:

Use list(map(...)) when you need a list for further operations like indexing or slicing.

3. Why This Matters:

Performance: Iterators can be more memory-efficient than lists, especially with large data sets.
Flexibility: Converting to a list is simple and explicit, so you only do it when truly necessary.

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Key Takeaway: In Python 3, map() yields an iterator for memory efficiency. Wrap your map() call with list() when a list structure is required.