itertools moudle

1. count(n): An infinite iterator will be created, so the above code will print out a sequence of natural numbers, which cannot be stopped at all. The iterator starts to iterate from n

example:

import  itertools
for n in  itertools.count(15):
print(n)
    if n == 20:
break            

15
16
17
18
19
20

2.cycle() will repeat the incoming sequence indefinitely:

>>> import itertools
>>> cs = itertools.cycle('ABC') # 注意字符串也是序列的一种
>>> for c in cs:
...     print(c)
...
'A'
'B'
'C'
'A'
'B'
'C'
...