python怎么判断字符串是否包含某些字符

>>> s='nihao,shijie'

>>> t='nihao'

>>> result = t in s

>>> print result

True

>>> import string

>>> s='nihao,shijie'

>>> t='nihao'

>>> result = string.find(s,t)!=-1

>>> print result

True

>>> result = string.rfind(s,t)!=-1

>>> print result

True

import string

def find_string(s,t):

    try:

        string.index(s,t)

        return True

    except(ValueError):

        return False

s='nihao,shijie'

t='nihao'

result = find_string(s,t)

print result  #True

>>> s='nihao,shijie'

>>> t='nihao'

>>> result = s.find(t)>=0

>>> print result

True

>>> result=s.count(t)>0

>>> print result

True

>>> result=s.index(t)>=0

>>> print result

True