Python Regex表达式失败 - 无法弄清楚原因

Question

I'm using:

re.search(r'^[A-Za-z0-9\:\(\) ]+\[[A-Za-z0-9\.]+\:[0-9]+\]$', log)

To search a log that looks like this:

"Logged at Thursday, March 20, 2014 20:48:03
FileVersion: 3.5.0.44954
ProductVersion: 3.5.0.44954
LogFile: Game.log

Exception Code: FATAL_ERROR
Exception Addr: 
Exception Module: 
Exception Description: FATAL_ERROR, 
Memory in use: 462.7MB
Debug Status: 
Out of Memory: 0

Call Stack Trace:
10) CSystem::FatalError()  [systemwin32.cpp:1267]
9) CFatalError()  [isystem.h:1528]

When I test the expression in Sublime Text/Notepad++, it succeeds. But when I run it as shown above in Python, I get nothing back.

Any ideas?

Answer 1

Use re.M for multiline regex matching.

re.search(r'^[A-Za-z0-9\:\(\) ]+\[[A-Za-z0-9\.]+\:[0-9]+\](?:[\n\r]|\Z)', log, re.M)
                                                              ^^^^^^^^

Also, this regex is checking for [\\n\\r] or \\Z at the end of regex instead of $ . FYI, \\Z means end of input string.

Answer 2

Elaborating on Sabuj Hassan's answer, the problem is simply that Python is not recognizing the end of the line as a terminal. This is because you are not using the MUTILINE flag , re.M .

Without this flag Python does not assign any special meaning to \\n characters and thus $ will only match the very end of the string. By including the re.M flag Python automatically adds terminals before all \\n characters, thus allowing $ to match both end-of-line and end-of-string.