如何修复python 3.7中的“运行时错误:字典在迭代期间更改大小”

original_dict = {'a': 1, 'b': 2, 'c': 3}
new_dict = {}

for key, value in original_dict.items():
    if key == 'b':
        new_dict[key] = 4
    else:
        new_dict[key] = value

original_dict.update(new_dict)

import copy

original_dict = {'a': 1, 'b': 2, 'c': 3}
copy_dict = copy.deepcopy(original_dict)

for key, value in copy_dict.items():
    if key == 'b':
        copy_dict[key] = 4

original_dict.update(copy_dict)

original_dict = {'a': 1, 'b': 2, 'c': 3}
keys_to_remove = []

for key, value in original_dict.items():
    if key == 'b':
        keys_to_remove.append(key)

for key in keys_to_remove:
    del original_dict[key]