Losing map value in variable

Question

Can’t understand why I can’t assign map result to a variable. It’s losing its value.

>>> L = 'something'
>>> R = map(lambda x: x * 2, L)
>>> print(list(R))
['ss', 'oo', 'mm', 'ee', 'tt', 'hh', 'ii', 'nn', 'gg']
>>> V = list(R)
>>> print(V)
[]

Asked By: John Doe

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Source

Answer 1

Because the map object can be iterated over only once. When you print it, that’s it. The next time you assign it, it’s empty

Instead, try

R = map(..)
V = list(R)
print(V)

Answered By: blue_note

Answer 2

In Python 3 map returns an iterator that, once consumed, will yield nothing.
In your case you are consuming it in the first print(list(R)) call, so in the second one it yields nothing which is the same as list() alone.

Answered By: Netwave

Losing map value in variable

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