sys build-in function
sys内建函数
chr()
bool()
cmp()
divmod()
enumerate()
file()
filter()
frozenset()
id()
int()
isinstance()
len()
list()
long()
map()
max()
min()
open()
ord()
pow()
raw_input()
reduce()
reload()
repr()
reversed()
round()
set()
sorted()
sum()
str(object)
tuple()
type()
zip()