str:查找的字符串
l_str:目标字符串
mi:开始查找的索引,起始点
def my_find(str,l_str,mi):
l = len(str)
for i in range(mi,len(l_str)):
if str[0] == l_str[i]:
if str == l_str[i:i+l]:
m_index = i
break
else:
m_index = -1
return m_index
s = '123sdas'
a = 's'
print(my_find(a,s,1))
3