Remove an item from a dictionary when its key is unknown

Question

What is the best way to remove an item from a dictionary by value, i.e. when the item\'s key is unknown? Here\'s a simple approach:

for key, item in some_di         


        

Answer 1

I'd build a list of keys that need removing, then remove them. It's simple, efficient and avoids any problem about simultaneously iterating over and mutating the dict.

keys_to_remove = [key for key, value in some_dict.iteritems()
                  if value == value_to_remove]
for key in keys_to_remove:
    del some_dict[key]