How to check if a given key already exists in a dictionary in Python?
You can use the in keyword to check if a key exists in a dictionary. For example:
my_dict = {'a': 1, 'b': 2, 'c': 3}
if 'a' in my_dict:
print("Key 'a' exists in the dictionary")
if 'd' in my_dict:
print("Key 'd' exists in the dictionary")
The first if statement will print "Key 'a' exists in the dictionary", but the second if statement will not execute because the key 'd' does not exist in the dictionary.
Alternatively, you can use the dict.get() method to check if a key exists in a dictionary. This method returns the value for the given key if it exists in the dictionary, and returns a default value (which you can specify) if the key does not exist. For example:
my_dict = {'a': 1, 'b': 2, 'c': 3}
value = my_dict.get('a') # value is 1
value = my_dict.get('d') # value is None
value = my_dict.get('d', 'default') # value is 'default'
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