These types were original factory functions, not types. So they got a lower name:
$ python1.5 Python 1.5.2 (#1, Apr 1 2009, 22:55:54) [GCC 4.1.2 20070925 (Red Hat 4.1.2-27)] on linux2 Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam >>> type(int) <type 'builtin_function_or_method'>
The fact that they are now types is a historical artifact anyway
All built-in types now follow this convention, including set and frozenset , which were added after the unification of the types that the types int et al.
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