重新排序使用字符串正則表達式

Question

我想帶日期的正則表達式或國內首個普遍發生，我的文字的開頭：

例子： "I went out on 1 sep 2012 and it was better than 15 jan 2012" ，我想 "1 sep 2012, I went out on and it was better than 15 jan 2012"

我在想用",1 sep 2012,"更換"1 sep 2012"，然後從","切斷繩子，但我不知道寫什麼，而不是replace_with：

line = re.sub(r'\d+\s(?:jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\s\d{4}', 'replace_with', line, 1) 

有幫助嗎？

Answer 1

使用capture groups：

>>> import re 
>>> s = "I went out on 1 sep 2012 and it was better than 15 jan 2012" 
>>> r = re.compile('(^.*)(1 sep 2012)(.*$)') 
>>> r.sub(r'\2\1\3',s) 
'1 sep 2012 I went out on and it was better than 15 jan 2012' 

支架捕捉部分字符串：

(^.*)   # Capture everything from the start of the string 
(1 sep 2012) # Upto the part we are interested in (captured) 
(.*$)   # Capture everything else 

然後，只需重新排序捕獲組替代`\2\1\3'注：引用捕獲組要求原料字符串r'\2\1\3'。在我的例子第二組僅僅是文字字符串(1 sep 2012)但當然也可以是任何正則表達式，如（上月底一個額外的\s）創建的一個：

(\d+\s(?:jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\s\d{4}\s) 

>>> r = re.compile(r'(^.*)(\d+\s(?:aug|sep|oct|nov)\s\d{4}\s)(.*$)') 
>>> r.sub(r'\2\1\3',s) 
'1 sep 2012 I went out on and it was better than 15 jan 2012' 

從docs.python.org：

當存在「r」或「R」前綴時，字符串中包含反斜槓後的字符而不更改。