Replace module level mutable containers with immutable containers

import sys
import importlib
import pkgutil
from collections import Counter

blacklist = ('idlelib.idle')
excluded_submodule_names = ('__main__')
search_submodules = 2
mutable_containers = (list, dict,  set)

def list_container_types(module, mcc):
    print_module = False
    for a in dir(module):
        if a in ('__all__', '__path__', '__builtins__', '__annotations__', '__conditional_annotations__'):
            # why is __all__ a list and not a tuple?
            continue
        # if not a.startswith('_'):
        #    continue
        attr = getattr(module, a)
        tp = type(attr)
        if issubclass(tp, mutable_containers):
            if not print_module:
                print(f'{module}:')
                print_module = True
            print(f'  {a}: {tp}')
            mcc.update([tp])


def search_modules(module_names, search_submodules: int, mcc):
    for name in module_names:
        if name in blacklist:
            continue
        try:
            module = importlib.import_module(name)
        except:
            print(f'{name}: error on import')
            module = None
        list_container_types(module, mcc)

        if search_submodules:
            try:
                sub_names = list(z.name for z in pkgutil.iter_modules(module.__path__))
            except Exception as ex:
                sub_names = []
            mm = [name + '.' + sub_name for sub_name in sub_names if sub_name not in excluded_submodule_names]
            search_modules(mm, search_submodules - 1, mcc)

mcc = Counter()
module_names = sorted(list(sys.builtin_module_names)) + sorted(list(sys.stdlib_module_names))
search_modules(module_names, search_submodules=2, mcc = mcc)

print()
print('number of module level containers by type:')
for key, value in mcc.items():
    print(f'{key}: {value}')