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                合規國際互聯網加速 OSASE為企業客戶提供高速穩定SD-WAN國際加速解決方案。 廣告
                #### python貪婪和非貪婪 Python里數量詞默認是貪婪的(在少數語言里也可能是默認非貪婪),總是嘗試匹配盡可能多的字符; 非貪婪則相反,總是嘗試匹配盡可能少的字符。 在"*","?","+","{m,n}"后面加上?,使貪婪變成非貪婪。 ~~~ >>> s="This is a number 234-235-22-423" >>> r=re.match(".+(\d+-\d+-\d+-\d+)",s) >>> r.group(1) '4-235-22-423' >>> r=re.match(".+?(\d+-\d+-\d+-\d+)",s) >>> r.group(1) '234-235-22-423' >>> ~~~ 正則表達式模式中使用到通配字,那它在從左到右的順序求值時,會盡量“抓取”滿足匹配最長字符串,在我們上面的例子里面,“.+”會從字符串的啟始處抓取滿足模式的最長字符,其中包括我們想得到的第一個整型字段的中的大部分,“\d+”只需一位字符就可以匹配,所以它匹配了數字“4”,而“.+”則匹配了從字符串起始到這個第一位數字4之前的所有字符。 解決方式:非貪婪操作符“?”,這個操作符可以用在"*","+","?"的后面,要求正則匹配的越少越好。 ~~~ >>> re.match(r"aa(\d+)","aa2343ddd").group(1) '2343' >>> re.match(r"aa(\d+?)","aa2343ddd").group(1) '2' >>> re.match(r"aa(\d+)ddd","aa2343ddd").group(1) '2343' >>> re.match(r"aa(\d+?)ddd","aa2343ddd").group(1) '2343' >>> ~~~ ~~~ # 提取網址:http://www.interoem.com/messageinfo.asp?id=35 # 為:http://www.interoem.com # 反向思維 >>>url = "http://www.interoem.com/messageinfo.asp?id=35" >>> re.sub(r"(http://.+?/).*", lambda x: x.group(1), url) 'http://www.interoem.com/' ~~~ ~~~ # 有一句英文如下: # hello world haibo # 查找所有的單詞 # 方法1 >>> s = "hello world haibo " >>> re.split(r" +", s) ['hello', 'world', 'haibo', ''] # 方法2 >>> re.findall(r"\b[a-zA-z]+\b", s) ['hello', 'world', 'haibo'] ~~~
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