转的！转的！！！

如果要将一个string list转换成int list (list里每个string都转成int)，比如

[python]  

['0','1','2'] -> [0,1,2]  

 

可以使用:

[python]   

[int(x) for x in list]  

 

或者使用map操作: map(func, list) 对list里的每个元素apply func.

[python]  

map(int, list)  

 

假设有一个2维数组（用list实现）:

[python]  

list = [[0,1,2],[3,1,4]]  

 

如果要得到每行之和，可以用以下两种方式：

[python]  

>>> list = [[0,1,2],[3,1,4]]  

>>> [sum(x) for x in list]  

[3, 8]  

>>> map(sum,list)  

[3, 8]  

 

如果要得到每列之和，需要用zip(*list)先unzip list,得到一个元组list，其中第i个元组包含了每行的第i个元素:

[python]  

>>> list = [[0,1,2],[3,1,4]]  

>>> zip(*list)  

[(0, 3), (1, 1), (2, 4)]  

>>> [sum(x) for x in zip(*list)]  

[3, 2, 6]  

>>> map(sum,zip(*list))  

[3, 2, 6]  

 

下面的例子是关于zip和unzip(其实是zip和*一起用)如何work的：

[python] 

>>> x=[1,2,3]  

>>> y=[4,5,6]  

>>> zipped = zip(x,y)  

>>> zipped  

[(1, 4), (2, 5), (3, 6)]  

>>> x2,y2=zip(*zipped)  

>>> x2  

(1, 2, 3)  

>>> y2  

(4, 5, 6)  

>>> x3,y3=map(list,zip(*zipped))  

>>> x3  

[1, 2, 3]  

>>> y3  

[4, 5, 6]