re.match() multiple times in the same string with Python

Question

I have a regular expression to find :ABC:`hello` pattern. This is the code.

format =r".*\:(.*)\:\`(.*)\`"
patt = re.compile(format, re.I|re.U)
m = patt.match(l.rstrip())
if m:
    ...

It works well when the pattern happens once in a line, but with an example ":tagbox:`Verilog` :tagbox:`Multiply` :tagbox:`VHDL`". It finds only the last one.

How can I find all the three patterns?

EDIT

Based on Paul Z's answer, I could get it working with this code

format = r"\:([^:]*)\:\`([^`]*)\`"
patt = re.compile(format, re.I|re.U)
for m in patt.finditer(l.rstrip()):
    tag, value = m.groups()  
    print tag, ":::", value

Result

tagbox ::: Verilog
tagbox ::: Multiply
tagbox ::: VHDL

Paul Z · Accepted Answer · 2011-03-16 03:10:28Z

9

Yeah, dcrosta suggested looking at the re module docs, which is probably a good idea, but I'm betting you actually wanted the finditer function. Try this:

format = r"\:(.*)\:\`(.*)\`"
patt = re.compile(format, re.I|re.U)
for m in patt.finditer(l.rstrip()):
    tag, value = m.groups()
    ....

Your current solution always finds the last one because the initial .* eats as much as it can while still leaving a valid match (the last one). Incidentally this is also probably making your program incredibly slower than it needs to be, because .* first tries to eat the entire string, then backs up character by character as the remaining expression tells it "that was too much, go back". Using finditer should be much more performant.

answered Mar 16, 2011 at 3:10

Paul Z

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1 Comment

prosseek Over a year ago

The regex should be format = r"\:([^:]*)\:`([^]*)`"` to make it work. After the change it works fine. Thanks.

Stuart Woodward · Accepted Answer · 2021-03-12 08:55:28Z

2

A good place to start is there module docs. In addition to re.match (which searches starting explicitly at the beginning of the string), there is re.findall (finds all non-overlapping occurrences of the pattern), and the methods match and search of compiled RegexObjects, both of which accept start and end positions to limit the portion of the string being considered. See also split, which returns a list of substrings, split by the pattern. Depending on how you want your output, one of these may help.

edited Mar 12, 2021 at 8:55

Stuart Woodward

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answered Mar 16, 2011 at 3:02

dcrosta

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Comments

ntg · Accepted Answer · 2021-03-23 21:18:31Z

0

re.findall or even better regex.findall can do that for you in a single line:

import regex as re #or just import re
s = ":tagbox:`Verilog` :tagbox:`Multiply` :tagbox:`VHDL`"
format = r"\:([^:]*)\:\`([^`]*)\`"
re.findall(format,s)

result is:

[('tagbox', 'Verilog'), ('tagbox', 'Multiply'), ('tagbox', 'VHDL')]

answered Mar 23, 2021 at 21:18

ntg

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