smichr/sympy — comment on commit b6d1cade952c955525633753fad3d3466512b2f4
File: sympy/core/mul.py line 1073
By asmeurer:

Just for future reference, you should have used `==`, not `is` here, as `is` comparison of small integers is just an implementation detail of CPython, and would break in something like PyPy.