Convert a list with strings all to lowercase or uppercase

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Track title: Puzzle Island

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Chapters
00:00 Question
00:23 Accepted answer (Score 616)
00:43 Answer 2 (Score 67)
01:09 Answer 3 (Score 67)
01:19 Answer 4 (Score 21)
01:46 Thank you

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Full question
https://stackoverflow.com/questions/1801...

Accepted answer links:
[list comprehensions]: https://docs.python.org/3/tutorial/datas...
[map]: https://docs.python.org/3/library/functi...

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https://meta.stackexchange.com/help/lice...

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Tags
#python #list

#avk47

ACCEPTED ANSWER

Score 672

It can be done with list comprehensions

>>> [x.lower() for x in ["A", "B", "C"]]
['a', 'b', 'c']
>>> [x.upper() for x in ["a", "b", "c"]]
['A', 'B', 'C']

or with the map function

>>> list(map(lambda x: x.lower(), ["A", "B", "C"]))
['a', 'b', 'c']
>>> list(map(lambda x: x.upper(), ["a", "b", "c"]))
['A', 'B', 'C']

ANSWER 2

Score 77

>>> list(map(str.lower,["A","B","C"]))
['a', 'b', 'c']

ANSWER 3

Score 68

Besides being easier to read (for many people), list comprehensions win the speed race, too:

$ python2.6 -m timeit '[x.lower() for x in ["A","B","C"]]'
1000000 loops, best of 3: 1.03 usec per loop
$ python2.6 -m timeit '[x.upper() for x in ["a","b","c"]]'
1000000 loops, best of 3: 1.04 usec per loop

$ python2.6 -m timeit 'map(str.lower,["A","B","C"])'
1000000 loops, best of 3: 1.44 usec per loop
$ python2.6 -m timeit 'map(str.upper,["a","b","c"])'
1000000 loops, best of 3: 1.44 usec per loop

$ python2.6 -m timeit 'map(lambda x:x.lower(),["A","B","C"])'
1000000 loops, best of 3: 1.87 usec per loop
$ python2.6 -m timeit 'map(lambda x:x.upper(),["a","b","c"])'
1000000 loops, best of 3: 1.87 usec per loop

ANSWER 4

Score 22

List comprehension is how I'd do it, it's the "Pythonic" way. The following transcript shows how to convert a list to all upper case then back to lower:

pax@paxbox7:~$ python3
Python 3.5.2 (default, Nov 17 2016, 17:05:23) 
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.

>>> x = ["one", "two", "three"] ; x
['one', 'two', 'three']

>>> x = [element.upper() for element in x] ; x
['ONE', 'TWO', 'THREE']

>>> x = [element.lower() for element in x] ; x
['one', 'two', 'three']