Python中的字符串查找操作方法总结

str = 'a,hello' 
print str.find('hello') # 在字符串str里查找字符串hello 
>> 2 # 

target = 'abb aba'
pattern = 'aba'

def match(target, pattern):
 i = j = 0
 n, m = len(target), len(pattern)
 while i < n and j < m:
 # 如果字符相等则目标和模板的下标都向右移
 if target[i] == pattern[j]:
 i, j = i+1, j+1
 else:
 # 如果字符不相等则目标下标切换到不相等的下标
 # 模板下标移动到初始下标
 i = i - j + 1
 j = 0
 if j == m:
 return i - j
 return -1

#修改的地方
else:
 i = i -j + 1
 j = 0
 print(target[i], pattern[j], i, j)

# 打印结果
b a 1 0
b a 2 0
 a 3 0
a a 4 0

def match(target, pattern):
 i = j = 0
 n, m = len(target), len(pattern)
 while i < n and j < m:
 # 如果字符相等则目标和模板的下标都向右移
 if if j == -1 and target[i] == pattern[j]:
 i, j = i+1, j+1
 else:
 # 这里通过next 函数来判断位移个数
 i = i - j + pattern_next(pattern[:j])
 j = 0
 if j == m:
 return i - j
 return -1


def pattern_next(s): 
 prefix = [s[:i+1] for i in range(len(s)-1)]
 suffix = [s[i+1:] for i in range(len(s)-1)]
 l = list(set(prefix) & set(suffix))
 return len(l)