The __index__() special method was introduced to make other integer-like types which are not int subclasses to be accepted as integer arguments.

It is supported by all PyArg_Parse format units for integers, except k (long sized bitfield) and K (long long sized bitfield). Argument Clinic has the same behavior for unsigned_long(bitwise=True) and unsigned_long_long(bitwise=True). It supports also non-bitwise unsigned integer converters, all of them do not support __index__().

Note that making PyLong_AsUnsignedLong() and PyLong_AsUnsignedLongLong() to support __index__() is potentially unsafe. But the higher level code that uses them, can be changed.

Linked PRs

• gh-132987: Support __index__() for "k" and "K" formats in PyArg_Parse #132988
• gh-132987: Support __index__() for unsigned integers in Argument Clinic #133011
• gh-132987: Support __index__() in the socket module #133093
• gh-132987: Support __index__() in the select.kqueue_event constructor #133094
• gh-132987: Support __index__() in the posix module #133096
• gh-132987: Support __index__() in the stat module #133097
• gh-132987: Support __index__() in the ssl.SSLContext.options setter #133098
• gh-132987: Support __index__() in the lzma module #133099
• gh-132987: Support __index__() in hashlib.scrypt() #133100