Python正则表达式：设置前缀长度的组合

Question

我试图找到字符串中的一组字符的所有组合，但发现的字符集必须具有特定的长度。我曾想过使用set函数[]和函数{：}的出现次数，我似乎无法让它们一起工作。

示例应该返回'this'和'hit'

谢谢。

def test_patterns(text, patterns=[]): 
    """Given source text and a list of patterns, look for 
    matches for each pattern within the text and print 
    them to stdout. 
    """ 
    # Look for each pattern in the text and print the results 
    for pattern, desc in patterns: 
     print "Pattern %r (%s)\n" % (pattern, desc) 
     print ' %r' % text 
     for match in re.finditer(pattern, text): 
      s = match.start() 
      e = match.end() 
      #substr = match.group() 
      substr = text[s:e] 
      n_backslashes = text[:s].count('\\') 
      prefix = '.' * (s + n_backslashes) 
      print ' %s%r' % (prefix, substr) 
     print 
    return 
if __name__ == '__main__': 
    test_patterns('Does this text contain hits or matches?', [('[this]{4:4}+', "Description"),]) 
raw_input() 

Answer 1

的quatifier {m} quatifies以下正则表达式m倍

例如

>>> st="Does this text contain hits or matches" 
>>> re.findall(r'[this]{4}', st) 
['this', 'hits'] 

或者更具体

>>> re.findall(r'\b[this]{4}\b', st) 
['this', 'hits'] 

其是相同书写

>>> re.findall(r'\b[this]{4,4}\b', st) 
['this', 'hits']