In this blog you will learn the basics of how to use the Python dictionary.
By the end of the tutorial you will be able to - Create Dictionaries - Get values in a Dictionary - Add and delete elements in a Dictionary - To and For Loops in a Dictionary
For example, you can have the fields “city”, “name,” and “food” for keys in a dictionary and assign the key, value pairs to the dictionary variable person1_information.
>>> type(person1_information)
{'city': 'San Francisco', 'name': 'Sam', 'food': 'shrimps'}
So, in the following example, a dictionary is initialized with keys “city”, “name,” and “food” and you can retrieve the value corresponding to the key “city.”
>>> person1_information = {'city': 'San Francisco', 'name': 'Sam', "food":"shrimps"}
>>> print the dictionary
>>> print(person1_information["city"])
San Francisco
>>> alphabets = {1: ‘a’}
>>> # get the value with key 1
>>> print(alphabets.get(1))
'a'
>>> # get the value with key 2. Pass “default” as default. Since key 2 does not exist, you get “default” as the return value.
>>> print(alphabets.get(2, "default"))
'default'
>>> # get the value with key 2 through direct referencing
>>> print(alphabets[2])
Traceback (most recent call last):
File "stdin", line 1, in module KeyError: 2
>>> for k, v in person1_information.items():
... print("key is: %s" % k)
... print("value is: %s" % v)
... print("###########################")
... key is: food
value is: shrimps
###########################
key is: city
value is: San Francisco
###########################
key is: name
value is: Sam
###########################
>>> person1_information = {}
>>> # add the key, value information with key “city”
>>> person1_information["city"] = "San Francisco"
>>> # print the present person1_information
>>> print(person1_information)
{'city': 'San Francisco'}
>>> # add another key, value information with key “name”
>>> person1_information["name"] = "Sam"
>>> # print the present dictionary
>>> print(person1_information)
{'city': 'San Francisco', 'name': 'Sam'}
>>> # add another key, value information with key “food”
>>> person1_information["food"] = "shrimps"
>>> # print the present dictionary
>>> print(person1_information)
{'city': 'San Francisco', 'name': 'Sam', 'food': 'shrimps'}
>>> person1_information = {'city': 'San Francisco'}
>>> # print it and check the present elements in the dictionary
>>> print(person1_information)
{'city': 'San Francisco'}
>>> # have a different dictionary
>>> remaining_information = {'name': 'Sam', "food": "shrimps"}
>>> # add the second dictionary remaining_information to personal1_information using the update method
>>> person1_information.update(remaining_information)
>>> # print the current dictionary
>>> print(person1_information)
{'city': 'San Francisco', 'name': 'Sam', 'food': 'shrimps'}
>>> person1_information = {'city': 'San Francisco', 'name': 'Sam', "food": "shrimps"}
>>> # delete the key, value pair with the key “food”
>>> del person1_information["food"]
>>> # print the present personal1_information. Note that the key, value pair “food”: “shrimps” is not there anymore.
>>> print(person1_information)
{'city': 'San Francisco', 'name': 'Sam'}
>>> person1_information = {'city': 'San Francisco', 'name': 'Sam', "food": "shrimps"}
>>> # deleting a non existent key gives key error.
>>> del person1_information["non_existent_key"]
Traceback (most recent call last):
File "", line 1, in
KeyError: 'non_existent_key'
>>> person1_information = {'city': 'San Francisco', 'name': 'Sam', "food": "shrimps"}
>>> # remove a key, value pair with key “food” and default value None
>>> print(person1_information.pop("food", None))
'Shrimps'
>>> # print the updated dictionary. Note that the key “food” is not present anymore
>>> print(person1_information)
{'city': 'San Francisco', 'name': 'Sam'}
>>> # try to delete a nonexistent key. This will return None as None is given as the default value.
>>> print(person1_information.pop("food", None))
None