pypa/pip · error · ValueError

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

Error message

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

What it means

Raised by iglob() when brace set markers '{' and '}' are mismatched (matched by _CHECK_MISMATCH_SET). distlib supports brace expansion like '{src,tests}/*.py' but rejects patterns with an unmatched '}' at the start or an unmatched '{' with no closing '}', raising ValueError 'mismatching set marker'.

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 == '':

View on GitHub (pinned to d7d0d0a394)

Solutions

1. Balance the braces: 'src/{a,b}/*.py'.
2. If you did not intend a set, remove the stray '{' or '}'.
3. Count '{' and '}' in the pattern and ensure they are equal and properly nested.

Example fix

// before
list(iglob('src/{a,b/*.py'))
// after
list(iglob('src/{a,b}/*.py'))

def safe_iglob(pattern):
    if pattern.count('{') != pattern.count('}'):
        raise ValueError('unbalanced brace set markers: %r' % pattern)
    from distlib.util import iglob
    return list(iglob(pattern))

from distlib.util import iglob
try:
    matches = list(iglob(pattern))
except ValueError as e:
    if 'mismatching set marker' in str(e):
        pattern = pattern.replace('{', '').replace('}', '')  # or fix brackets
        matches = list(iglob(pattern))
    else:
        raise

When it happens

Trigger: iglob('src/{a,b/*.py') (missing '}'), iglob('src/a,b}/x') (missing '{'), or any pattern where braces are unbalanced.

Common situations: Programmatic glob construction that omits a brace, copy-paste from configs that stripped a brace, or escaping mistakes.

Related errors

• invalid glob %r: recursive glob "**" must be used alone
• {req_name} does not appear to be a Python project: neither '
• Directory {name!r} is not installable. Neither 'setup.py' no
• Invalid requirement: {req_as_string!r}: {exc}
• Invalid requirement: {req_string!r}: {exc}

AI-assisted analysis of pypa/pip@d7d0d0a394 (2026-08-04). Data as JSON: /data/errors/fb6116844a3110b6.json. Report an issue: GitHub.