Check if a given key already exists in a dictionary

To check if a given key already exists in a dictionary, you can use the in keyword. For example:

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

if 'a' in my_dict:
    print("Key 'a' exists in dictionary")
else:
    print("Key 'a' does not exist in dictionary")

This will output Key 'a' exists in dictionary. If you want to check if a key does not exist in the dictionary, you can use the not in keyword.

For example:

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

if 'd' not in my_dict:
    print("Key 'd' does not exist in dictionary")
else:
    print("Key 'd' exists in dictionary")

This will output Key 'd' does not exist in dictionary.