python100例编程python100例核心知识你知道多少python100例子
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资料目录
Python练习集100题
100道Python面试题
Python100经典练习题
Python经典题目100道题
Python题库(已收录100道真题）
Python100例视频讲解课程
菜鸟教程Python教程100例
130道python练习题，涵盖基础内容的方方面面
举例 replace
def my_replace(source, oldsub, newsub):
"""
将字符串里所有的oldsub子串替换成newsub
:param source:
:param old:
:param new:
:return:
"""
if not source or not oldsub:
return source
new_string = ""
start_index = 0
index = my_find(source, oldsub, start=start_index)
while index != -1:
new_string += source[start_index:index] + newsub
start_index = index+len(oldsub)
index = my_find(source, oldsub, start=start_index)
new_string += source[start_index:]
return new_string
def my_find(source, target, start=0):
"""
返回字符串source中 子串target开始的位置， 从start索引开始搜索
如果可以找到多个，返回第一个
:param source:
:param target:
:param start:
:return:
"""
if not source or not target:
return -1
# 不合理的搜索起始位置
if start < 0 or start >= len(source):
return -1
if len(target) > len(source):
return -1
for index in range(start, len(source) - len(target)+1):
t_index = 0
while t_index < len(target):
if target[t_index] == source[t_index+index]:
t_index += 1
else:
break
if t_index == len(target):
return index
return -1
if __name__ == '__main__':
print(my_replace('this is a book', 'this', 'it'))
print(my_replace('this is a this book', 'this', 'it'))
print(my_replace('this is a this bookthis', 't2his', 'it'))
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