Question

I want to be able to replace a string in a file using regular expressions. But my function isn’t finding a match. So I’ve mocked up a test to replicate what’s happening.

I have defined the string I want to replace as follows:

string = 'buf = O_strdup("ONE=001&TYPE=PUZZLE&PREFIX=EXPRESS&");'

I want to replace the “TYPE=PUZZLE&PREFIX=EXPRESS&” part with something else. NB. the string won’t always contain exactly “PUZZLE” and “PREFIX” in the original file, but it will be of that format ).

So first I tried testing that I got the correct match.

 obj = re.search(r'TYPE=([\^&]*)\&PREFIX=([\^&]*)\&', string)
 if obj:
    print obj.group()
 else:
    print "No match!!"

Thinking that ([\^&]*) will match any number of characters that are NOT an ampersand.
But I always get “No match!!”.

However,
obj = re.search(r'TYPE=([\^&]*)', string)

returns me “TYPE=”

Why doesn’t my first one work?

Answer 1

Since the ^ sign is escaped with \ the following part: ([\^&]*) matches any sequence of these characters: ^, &.

Try replacing it with ([^&]*).