# map函数

\$ pydoc map

map(...)
map(function, sequence[, sequence, ...]) -> list

Return a list of the results of applying the function to the items of
the argument sequence(s).  If more than one sequence is given, the
function is called with an argument list consisting of the corresponding
item of each sequence, substituting None for missing values when not all
sequences have the same length.  If the function is None, return a list of
the items of the sequence (or a list of tuples if more than one sequence).


map函数是对参数sequnce里的所有元素执行function函数，然后将结果返回到一个列表中。这很像R语言中的lapply(x,FUN)函数。

s = ['1', '2', '3']
print sum(s)

TypeError: unsupported operand type(s) for +: 'int' and 'str'

s = ['1', '2', '3']
s1 = map(int,s)
print sum(s1)

6