1、自定义字符串的count函数

>>> s = "Abcdb"
>>> s.count("b")
2
>>> s.count("bc")
1
>>> s.count("bd")
0
>>>

#可以包含重叠的字符
def str_count(string,sub_str):
    if (not isinstance(string,str)) or (not isinstance(sub_str,str)):
        return "string或sub_str不是字符串类型"
    sub_count = 0
    sub_len = len(sub_str)
    #遍历
    for i in range(len(string)):
        if string[i:i+sub_len] == sub_str:
            sub_count += 1
    return sub_count

print(str_count("Abcbcb","b"))
print("Abcbcb".count("b"))
print(str_count("Abcbcb","bc"))
print("Abcbcb".count("bc"))
print(str_count("bcbcb","bcb"))
print("Abcbcb".count("bcb"))
print(str_count("bcbcb123","123"))
print("bcbcb123".count("123"))
print(str_count("bcbcb123",int("123")))
print(