toms515, a Python code which lists the subsets of size K selected from a set of size N, by Bill Buckles, Matthew Lybanon.
The text of many ACM TOMS algorithms is available online through ACM: https://calgo.acm.org/ or NETLIB: https://www.netlib.org/toms/index.html.
The computer code and data files made available on this web page are distributed under the GNU LGPL license.
toms515 is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version and a Python version.
SUBSET, a Python code which enumerates combinations, partitions, subsets, index sets, and other combinatorial objects.
Original FORTRAN77 version by Bill Buckles, Matthew Lybanon. Python version by John Burkardt.