列表理解是我的做法，这是“python”的方式。下面的文字记录展示了如何将一个列表全部转换为大写，然后再转换回小写:

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']

mylist = ['Mixed Case One', 'Mixed Case Two', 'Mixed Three']
print(list(map(lambda x: x.lower(), mylist)))
print(list(map(lambda x: x.upper(), mylist)))

对于这个例子，理解是最快的

$ python -m timeit -s 's=["one","two","three"]*1000' '[x.upper for x in s]'
1000 loops, best of 3: 809 usec per loop

$ python -m timeit -s 's=["one","two","three"]*1000' 'map(str.upper,s)'
1000 loops, best of 3: 1.12 msec per loop

$ python -m timeit -s 's=["one","two","three"]*1000' 'map(lambda x:x.upper(),s)'
1000 loops, best of 3: 1.77 msec per loop

你可以尝试使用:

my_list = ['india', 'america', 'china', 'korea']

def capitalize_list(item):
    return item.upper()

print(list(map(capitalize_list, my_list)))

如果你的目的是通过一次转换来匹配另一个字符串，你也可以使用str.casefold()。

这是有用的，当你有非ascii字符和匹配ascii版本(例如:maße vs masse)。虽然str.lower或str.upper在这种情况下失败，但str.casefold()将通过。 这在Python 3中可用，详细讨论了这个想法，答案是https://stackoverflow.com/a/31599276/4848659。

>>>str="Hello World";
>>>print(str.lower());
hello world
>>>print(str.upper());
HELLO WOLRD
>>>print(str.casefold());
hello world

列表理解是我的做法，这是“python”的方式。下面的文字记录展示了如何将一个列表全部转换为大写，然后再转换回小写:

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']