CODEWITHSUNDEEP
pythonregex
dgel
dgel

Reputation: 16796

Best pythonic way to insert quotes into a string

I'm dealing with this python bug while writing my own reverse proxy. The server is sending my proxy this Set-Cookie response header:

workgroup_session_id=ilDJtR0rE1AG28C9ZxKLHj8TBtcT89sw; Path=/; Expires=Sun, 02-Dec-2012 5:57:25 GMT; HttpOnly

I am loading this string into a SimpleCookie instance from the Cookie module. Unfortunately, because of the bug that I referenced above, when I later pull expires out of the morsel dictionary it returns Sun,. I have found that I can overcome this bug by adding quotes around the Expires component of the Set-Cookie header (or adding quotes around any key / value pair that contains spaces in the value).

So this:

workgroup_session_id=ilDJtR0rE1AG28C9ZxKLHj8TBtcT89sw; Path=/; Expires=Sun, 02-Dec-2012 5:57:25 GMT; HttpOnly

Would become: 

workgroup_session_id=ilDJtR0rE1AG28C9ZxKLHj8TBtcT89sw; Path=/; Expires="Sun, 02-Dec-2012 5:57:25 GMT"; HttpOnly

And this:

test=a b c; Path=/; Expires=a b c; HttpOnly

Would become:

test="a b c"; Path=/; Expires="a b c"; HttpOnly

I know that I could break the string into tokens and loop through them looking for spaces, then reconstruct the string, but I am curious what the best performing solution would be. As I mentioned, this is a reverse proxy that could potentially handle a few hundred requests a second, so I'd like this substitution to be as fast as possible.

Would a regular expression substitution (pre-compiled of course) be efficient? I've heard that regular expressions are pretty heavy....

Upvotes: 0

Views: 128

Answers (2)

Tim Pietzcker
Tim Pietzcker

Reputation: 336128

How about this regex:

import re
header = re.sub("(?<==)[^;]* [^;]*", r'"\g<0>"', header)

This inserts quotes around whatever follows after a = until the next ; (or end of string), but only if there is at least one space in-between.

>>> header = 'test=a b c; Path=/; Expires=a b c; HttpOnly'
>>> re.sub("(?<==)[^;]* [^;]*", r'"\g<0>"', header)
'test="a b c"; Path=/; Expires="a b c"; HttpOnly'
>>> header = "workgroup_session_id=ilDJtR0rE1AG28C9ZxKLHj8TBtcT89sw; Path=/; Expires=Sun, 02-Dec-2012 5:57:25 GMT; HttpOnly"
>>> re.sub("(?<==)[^;]* [^;]*", r'"\g<0>"', header)
'workgroup_session_id=ilDJtR0rE1AG28C9ZxKLHj8TBtcT89sw; Path=/; Expires="Sun, 02-Dec-2012 5:57:25 GMT"; HttpOnly'

Upvotes: 1

khagler
khagler

Reputation: 4056

Do you need to put quotes just around the date following Expires, or any arbitrary date that appears anywhere in the header? If it's the former, try this:

header = "workgroup_session_id=ilDJtR0rE1AG28C9ZxKLHj8TBtcT89sw; Path=/; Expires=Sun, 02-Dec-2012 5:57:25 GMT; HttpOnly"
print(header.replace('Expires=', 'Expires="').replace('GMT', 'GMT"'))

Upvotes: 1

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