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2014-08-01 23:06:37
I think you mean to use map instead of filter:
>>> from string import upper
>>> mylis=['this is test', 'another test']
>>> map(upper, mylis)
['THIS IS TEST', 'ANOTHER TEST']
Even simpler, you could use str.upper instead of importing from string (thanks to @alecxe):
>>> map(str.upper, mylis)
['THIS IS TEST', 'ANOTHER TEST']
In Python 2.x, map constructs a new list by applying a given function to every element in a list. filter constructs a new list by restricting to elements that evaluate to True with a given function.
In Python 3.x, map and filter construct iterators instead of lists, so if you are using Python 3.x and require a list the list comprehension approach would be better suited.
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map(str.upper, mylis)would work too, would help to avoid astringimport.Note that
maponly constructs aliston python2.x -- On python3.x it returns an iterator. Frequently that doesn't matter, but if you need a list as output, then it's probably better to use a list comprehension as in the other answer.Is approach the same for side effecting functions?
In Python 3.x, you can do
list(map(str.upper, mylis)), if you want list.