pypa/pip · error · ValueError

invalid glob %r: mismatching set marker

Error message

invalid glob %r: mismatching set marker '{' or '}'

What it means

Raised as ValueError by distlib.util.iglob when the pattern has mismatched set markers '{' or '}'. The regex _CHECK_MISMATCH_SET matches a '}' with no preceding '{' in the leading portion, or a '{' with no following '}' to the end — i.e. unbalanced brace-set syntax. The extended globber uses '{a,b,c}' for alternation sets; an orphan brace cannot be parsed.

Solutions

1. Ensure every '{' has a matching '}' and they are correctly ordered.
2. Validate brace balance before calling: pattern.count('{') == pattern.count('}').
3. Build alternation sets from a list and format with '{%s}' % ','.join(options).

Example fix

# before
iglob('tests/{unit,integration')
# after
iglob('tests/{unit,integration}')

def valid_glob(pattern):
    return pattern.count('{') == pattern.count('}') and '}' not in pattern.split('{')[0]

def has_balanced_braces(s: str) -> bool:
    return isinstance(s, str) and s.count('{') == s.count('}')

try:
    list(iglob(pattern))
except ValueError as e:
    if 'mismatching set marker' in str(e):
        pattern += '}' if pattern.count('{') > pattern.count('}') else ''

When it happens

Trigger: iglob('src/{python,ruby'), iglob('src/python}'), or any pattern where '{' and '}' counts are unbalanced or appear out of order. Valid 'src/{a,b}/c' is accepted.

Common situations: Dynamically building alternation sets and dropping a closing brace; config-supplied glob patterns with typos; concatenating partial patterns that break brace nesting.

Related errors

• invalid glob %r: recursive glob "**" must be used alone
• file '%r' does not exist
• path ' ' cannot be absolute
• path ' ' cannot end with '/
• which would be overwritten

AI-assisted analysis of pypa/pip@f399c37189 (2026-08-08). Data as JSON: /api/errors/fb6116844a3110b6. Report an issue: GitHub.

Appendix: source

Thrown at src/pip/_vendor/distlib/util.py:1441

#
# Glob functionality
#

RICH_GLOB = re.compile(r'\{([^}]*)\}')
_CHECK_RECURSIVE_GLOB = re.compile(r'[^/\\,{]\*\*|\*\*[^/\\,}]')
_CHECK_MISMATCH_SET = re.compile(r'^[^{]*\}|\{[^}]*$')


def iglob(path_glob):
    """Extended globbing function that supports ** and {opt1,opt2,opt3}."""
    if _CHECK_RECURSIVE_GLOB.search(path_glob):
        msg = """invalid glob %r: recursive glob "**" must be used alone"""
        raise ValueError(msg % path_glob)
    if _CHECK_MISMATCH_SET.search(path_glob):
        msg = """invalid glob %r: mismatching set marker '{' or '}'"""
        raise ValueError(msg % path_glob)
    return _iglob(path_glob)


def _iglob(path_glob):
    rich_path_glob = RICH_GLOB.split(path_glob, 1)
    if len(rich_path_glob) > 1:
        assert len(rich_path_glob) == 3, rich_path_glob
        prefix, set, suffix = rich_path_glob
        for item in set.split(','):
            for path in _iglob(''.join((prefix, item, suffix))):
                yield path
    else:
        if '**' not in path_glob:
            for item in std_iglob(path_glob):
                yield item
        else:
            prefix, radical = path_glob.split('**', 1)
            if prefix == '':

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