The way Python 3 handles identifiers containing mathematical characters appears to be broken. I didn't test the entire range of U+1D400 through U+1D59F but I spot-checked them and the bug manifests itself there:

    Python 3.9.7 (default, Sep 10 2021, 14:59:43) 
    [GCC 11.2.0] on linux
    Type "help", "copyright", "credits" or "license" for more information.

    >>> foo = 1234567890
    >>> bar = 1234567890
    >>> foo is bar
    False
    >>> 𝖇𝖆𝖗 = 1234567890

    >>> foo is 𝖇𝖆𝖗
    False
    >>> bar is 𝖇𝖆𝖗
    True

    >>> 𝖇𝖆𝖗 = 0
    >>> bar
    0


This differs from the behavior with other non-ASCII characters. For example, ASCII 'a' and Cyrillic 'a' are properly treated as different identifiers:

    >>> а = 987654321    # Cyrillic lowercase 'a', U+0430
    >>> a = 123456789    # ASCII 'a'
    >>> а        # Cyrillic
    987654321
    >>> a        # ASCII
    123456789


While a bit of a pathological case, it is a nasty surprise. It's possible this is a symptom of a larger bug in the way identifiers are resolved.

This is similar but not identical to https://bugs.python.org/issue46555

Note: I did not find this myself; I give credit to Cooper Stimson (https://github.com/6C1) for finding this bug. I merely reported it.

This seems coherent with https://www.python.org/dev/peps/pep-3131/ to me. The parser ensures all identifiers are converted into the normal form NFKC while parsing; comparison of identifiers is based on NFKC.

Please read "Identifiers and keywords" [1] in the documentation. For example:

    >>> import unicodedata as ud
    >>> ud.normalize('NFKC', '𝖇𝖆𝖗') == 'bar'
    True

    >>> c = '\N{CYRILLIC SMALL LETTER A}'
    >>> ud.name(ud.normalize('NFKC', c))
    'CYRILLIC SMALL LETTER A'

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[1] https://docs.python.org/3/reference/lexical_analysis.html?highlight=nfkc#identifiers

I did read PEP-3131 before posting this but I still thought the behavior was counterintuitive.