import linecache
import weakref
def gen_func(n):
    func_code = """
def func():
    pass
"""
    g = {}
    exec(func_code, g, g)
    func = g['func']
    filename = f"<generated-{n}>"
    linecache.cache[filename] = (len(func_code), None, func_code.splitlines(True), filename)
    def cleanup_linecache(filename):
        def _cleanup():
            if filename in linecache.cache:
                del linecache.cache[filename]
        return _cleanup
    weakref.finalize(func, cleanup_linecache(filename))
    return func
def main():
    n = 0
    while True:
        func = gen_func(n)
        del func
        linecache.checkcache()
        n += 1
        if n % 100000 == 0:
            print(n)
if __name__ == '__main__':
    main()

 ✘  graingert@conscientious  ~/projects/weakref-func-cycle-never-gc   main  python demo.py
Traceback (most recent call last):
  File "/home/graingert/projects/weakref-func-cycle-never-gc/demo.py", line 38, in <module>
    main()
  File "/home/graingert/projects/weakref-func-cycle-never-gc/demo.py", line 32, in main
    linecache.checkcache()
  File "/usr/lib/python3.12/linecache.py", line 64, in checkcache
    entry = cache[filename]
            ~~~~~^^^^^^^^^^
KeyError: '<generated-147>'
 ✘  graingert@conscientious  ~/projects/weakref-func-cycle-never-gc   main  phyt
 ✘  graingert@conscientious  ~/projects/weakref-func-cycle-never-gc   main  python3.13 demo.py
Traceback (most recent call last):
  File "/home/graingert/projects/weakref-func-cycle-never-gc/demo.py", line 38, in <module>
    main()
    ~~~~^^
  File "/home/graingert/projects/weakref-func-cycle-never-gc/demo.py", line 32, in main
    linecache.checkcache()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/usr/lib/python3.13/linecache.py", line 59, in checkcache
    entry = cache[filename]
            ~~~~~^^^^^^^^^^
KeyError: '<generated-2637>'