How to do a Reverse Dictionary Lookup in Python

A reverse dictionary lookup will return a list containing all the keys in a dictionary. Dictionary keys map values and are used to access values in dictionaries.


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

lookup_val = 1

all_keys = []
for key, value in dictionary.items():
   if(value == lookup_val):



Here is the same functionality but written with list comprehension so it fits on one line.


all_keys = [key for key, value in dictionary.items() if value == lookup_val]