源码: simple.py

# -.- coding:utf-8 -.-
#
# 检查一个字符是否包含另外一个字符.
#
# 相似功能, in 关键字, 举例:
# if "a" in "abc":
#     return True
# else:
#     return False


from __future__ import print_function


def in_(letters, find):
    """
    :return: True or False
    """
    # 字符集的总长度
    letters_len = len(letters)

    # 匹配关键字的总长度
    find_len = len(find)

    # 利用分片, 从
    # 0: 0+find_len
    # 1: 1+find_len
    # 2: 2+find_len
    # ...
    # 以此类推去查找.
    for i in range(letters_len):
        print(i)
        if letters[i:i+find_len] == find:
            return True

    # 未命中则返回False
    return False


if __name__ == '__main__':
    print(in_("abcdefg", "fg"))

# 一共查找了7次
# output
0
1
2
3
4
5
6
False

源码: optimize.py

# -.- coding:utf-8 -.-
#
# 检查一个字符是否包含另外一个字符.
#
# 相似功能, in 关键字, 举例:
# if "a" in "abc":
#     return True
# else:
#     return False


from __future__ import print_function


def in_(letters, find):
    letters_len = len(letters)
    find_len = len(find)
    max_index = letters_len - find_len

    for i in range(max_index + 1):
        print(i)
        if letters[i:i+find_len] == find:
            return True

    return False


if __name__ == '__main__':
    print(in_("abcdefg", "fg"))

# 一共查找了6次
# output
0
1
2
3
4
5
True

源码: final.py

# -.- coding:utf-8 -.-
# 检查一个字符是否包含另外一个字符.
from __future__ import print_function


# 不采用分片的写法.
def has_substring(search, find):
    if not search:
        return bool(find)

    max_search_index = len(search) - len(find)

    for i in range(0, max_search_index+1):
        found = True

        for j in range(0, len(find)):
            if search[i+j] != find[j]:
                found = False
                break

        if found:
            return found

    return False


if __name__ == '__main__':
    print(has_substring("abcdefg", "gh"))