Why does this regex not match in Python?

Question

I have the regular expression

(GET|POST) (/api/\w+) (HTTP/1\.\d)(?:.*\\r\\n\\r\\n)(\S+)?

which I'm trying to match against HTTP GET and HTTP POST requests. I'm using the helpful regex101.com website to format my regular expression, and according to it, the regular expression should match both the formats I'm seeking.

Here's my regular expression on regex101.com.

However, when I input into Python itself and call re.split(), (on an input of strings), it doesn't split the POST request. It only splits the GET request. I thought it had something to do with the way regex101 parses \r\n (CRLF) versus how Python does it, so I double-checked and made sure that in Python, I actually type in \r\n\ inside the regex, and not \\r\\n, as I did in regex101. Yet it still doesn't work.

How can I get the regular expression to work inside Python?

codebee · Accepted Answer · 2019-10-05 00:28:15Z

1

Your'e just missing an additional \r\n after HTTP/1.0. This will work:

'POST /api/gettime HTTP/1.0\r\n\r\nContent-Length: 13\r\n\r\n100000+200000'

answered Oct 5, 2019 at 0:28

codebee

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8 Comments

Alureon Over a year ago

OK, I see that now. Good catch. But I actually do need to have the POST format have only one \r\n after HTTP/1.0. So is there a way I can use one regex to handle both \r\n\ and \r\n\r\n? I'm fiddling around with the regular expression right now, but am not having much luck.

Nick Over a year ago

@WaterGuy (\r\n)+ will match one or more \r\n or (\r\n){1,2} to only match 1 or 2 occurrences

Alureon Over a year ago

@Nick I gave that a shot, and yet it didn't work. I tried (?:\\r\\n)+ and yet it only matched one \r\n.

Nick Over a year ago

@WaterGuy It's working for me on your regex101 page: regex101.com/r/Ghlo0L/4

Nick Over a year ago

@WaterGuy chalk it up to the ghost in the machine. Glad to hear it's working.

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