CODEWITHSUNDEEP
pythonregexregex-lookarounds
ehacinom
ehacinom

Reputation: 8894

Regex that grabs variable number of groups

This is not a question asking how to use re.findall() or the global modifier (?g) or \g. This is asking how to match n groups with one regex expression, with n between 3 and 5.

Rules:

My question is if this is doable, and how?

I've gotten this far, but it hasn't dealt with comments or unknown order or if some items are missing and to stop searching for this particular regex when you see the next class definition. https://www.regex101.com/r/cG5nV9/8

(?s)\nclass\s(.*?)(?=\()
.*?
model\s=\s(.*?)\n
.*?
(?=fields.*?\((.*?)\))
.*?
(?=write_once_fields.*?\((.*?)\))
.*?
(?=required_fields.*?\((.*?)\))

Do I need a conditional?

Thanks for any kinds of hints.

Upvotes: 3

Views: 818

Answers (1)

Adam Smith
Adam Smith

Reputation: 54213

I'd do something like:

from collections import defaultdict
import re

comment_line = re.compile(r"\s*#")
matches = defaultdict(dict)

with open('path/to/file.txt') as inf:
    d = {} # should catch and dispose of any matching lines
           # not related to a class
    for line in inf:
        if comment_line.match(line):
            continue # skip this line
        if line.startswith('class '):
            classname = line.split()[1]
            d = matches[classname]
        if line.startswith('model'):
            d['model'] = line.split('=')[1].strip()
        if line.startswith('fields'):
            d['fields'] = line.split('=')[1].strip()
        if line.startswith('write_once_fields'):
            d['write_once_fields'] = line.split('=')[1].strip()
        if line.startswith('required_fields'):
            d['required_fields'] = line.split('=')[1].strip()

You could probably do this easier with regex matching.

comment_line = re.compile(r"\s*#")
class_line = re.compile(r"class (?P<classname>)")
possible_keys = ["model", "fields", "write_once_fields", "required_fields"]
data_line = re.compile(r"\s*(?P<key>" + "|".join(possible_keys) +
                       r")\s+=\s+(?P<value>.*)")

with open( ...
    d = {} # default catcher as above
    for line in ...
       if comment_line.match(line):
           continue
       class_match = class_line.match(line)
       if class_match:
           d = matches[class_match.group('classname')]
           continue # there won't be more than one match per line
       data_match = data_line.match(line)
       if data_match:
           key,value = data_match.group('key'), data_match.group('value')
           d[key] = value

But this might be harder to understand. YMMV.

Upvotes: 1

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