Source: 📖 Effective Python item 16

Using get to check for existence of a key in a dict type

The get method implicitly searches for the existence of a key within the dict it is called on. If the key can be found, it returns the associated value; if the key can't be found, it returns None.

my_dict = {'name': 'juan', 'dob': '01/12/1995'}

name = my_dict.get('name')
gender = my_dict.get('gender')

print(name, gender)

>>>
juan None

An optional default return value can also be passed to get—note that this simply returns the given value; it does not create a new key in the dict.

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name = my_dict.get('name')
gender = my_dict.get('gender', 'not specified')

print(name, gender)
print(my_dict.keys())

>>>
juan not specified
dict_keys(['name', 'dob'])	# no new key created

Using get combined with := assignment expressions instead of testing if a key is in a dict and then using if/else control flow statements can make for cleaner, terser code.

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if not (gender := my_dict.get('gender')):
	gender = 'male'
	my_dict['gender'] = gender

See also:

• Assignment expressions explained