将一个Python列表全部转换为小写或大写
我有一个包含string的Python列表variables。 有一个python函数可以将所有string转换为小写，反之亦然，大写？
这可以通过列表parsing来完成
>>> [x.lower() for x in ["A","B","C"]] ['a', 'b', 'c'] >>> [x.upper() for x in ["a","b","c"]] ['A', 'B', 'C'] 或与地图function
>>> map(lambda x:x.lower(),["A","B","C"]) ['a', 'b', 'c'] >>> map(lambda x:x.upper(),["a","b","c"]) ['A', 'B', 'C']
除了易于阅读（对于许多人），列表parsing也赢得了速度竞赛：
$ 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
>>> map(str.lower,["A","B","C"]) ['a', 'b', 'c']
列表parsing是我怎么做的。 下面的代码片段展示了如何将列表转换为全部大写，然后再转换为更低：
$ python Python 2.5.2 (r252:60911, Dec 2 2008, 09:26:14) [GCC 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)] on cygwin Type "help", "copyright", "credits" or "license" for more information. >>> list = ["one", "two", "three"] >>> list ['one', 'two', 'three'] >>> list = [element.upper() for element in list] >>> list ['ONE', 'TWO', 'THREE'] >>> list = [element.lower() for element in list] >>> list ['one', 'two', 'three']
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循环，最好是每循环3：809次 $ python -m timeit -s's = [“one”，“two”，“three”] * 1000''map（str.upper，s）' 1000个循环，最好是3：1.12毫秒每个循环 $ python -m timeit -s's = [“one”，“two”，“three”] * 1000''map（lambda x：x.upper（），s）' 1000个循环，最好是3：1.77毫秒每个循环
mylist = ['Mixed Case One', 'Mixed Case Two', 'Mixed Three'] print map(lambda x: x.lower(), mylist) print map(lambda x: x.upper(), mylist)
一个学生问，另一个同样问题的学生回答:)）
fruits=['orange', 'grape', 'kiwi', 'apple', 'mango', 'fig', 'lemon'] newList = [] for fruit in fruits: newList.append(fruit.upper()) print(newlist)
