{"id":329317,"date":"2023-10-05T04:31:11","date_gmt":"2023-10-05T04:31:11","guid":{"rendered":"https:\/\/pythonguides.com\/?p=17344"},"modified":"2023-10-05T04:31:11","modified_gmt":"2023-10-05T04:31:11","slug":"python-dictionary-contains-6-example","status":"publish","type":"post","link":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/2023\/10\/05\/python-dictionary-contains-6-example\/","title":{"rendered":"Python Dictionary contains (6+ Example)"},"content":{"rendered":"

<\/p>\n

In this Python Tutorial, I will explain what the Python Dictionary contains<\/strong> means and how we can check what the dictionary contains in Python using different methods with examples.<\/p>\n

What does the Python Dictionary contains mean?<\/h2>\n

In Python, dictionaries are a flexible way to store and manipulate data. We use the term “Python Dictionary Contains<\/strong>” to describe the action of checking whether a specific key or value is present within a dictionary Python. In this article, we will go over various ways to determine if a dictionary contains a certain element, key, or value, with relevant examples.<\/p>\n

Python Dictionary Contains Key<\/h3>\n

To check if a Python dict contains a specific key, you can use the in keyword. This is an essential task because attempting to access a key that does not exist will result in a KeyError.<\/p>\n

For instance<\/strong>: Consider a program that needs to find the capital of a U.S. state. We have a dictionary of states and their capitals.<\/p>\n

states_capitals = {\n    'California': 'Sacramento',\n    'Texas': 'Austin',\n    'Florida': 'Tallahassee',\n}\n\nprint('California' in states_capitals)<\/code><\/pre>\n
Output:<\/strong> In this example, ‘California’ in states_capitals<\/strong> returns True<\/strong>, confirming that the dictionary contains the key ‘California<\/strong>‘.<\/p>\n
True<\/code><\/pre>\n
\n
\"Python<\/figure>\n<\/div>\n
Python Dictionary Contains Value<\/h3>\n
To verify if a Python dictionary contains the value, use the values()<\/strong> method followed by the in keyword.<\/p>\n
For example<\/strong>: Now, imagine you want to check if a specific city is the capital of any U.S. state in the above states_capitals<\/strong> dictionary in Python.<\/p>\n
states_capitals = {\n    'California': 'Sacramento',\n    'Texas': 'Austin',\n    'Florida': 'Tallahassee',\n}\n\nprint('Austin' in states_capitals.values())<\/code><\/pre>\n
Output: <\/strong>Here, ‘Austin<\/strong>‘ in states_capitals.values()<\/strong> returns True<\/strong>, indicating that ‘Austin<\/strong>‘ is a capital in the states_capitals<\/strong> dictionary in Python.<\/p>\n
True<\/code><\/pre>\n
\n
\"dictionary<\/figure>\n<\/div>\n
Python Dictionary Contains List as Value<\/h3>\n
Sometimes, a dictionary contains a list of values<\/strong> where the key is associated with a list of values.<\/p>\n
For instance<\/strong>, In a program keeping track of major cities in each state, you want to check if a particular city is in the list of major cities for a specific state.<\/p>\n
states_cities = {\n    'California': ['Los Angeles', 'San Francisco', 'San Diego'],\n    'Texas': ['Houston', 'Dallas', 'San Antonio'],\n}\n\nprint('San Francisco' in states_cities['California'])<\/code><\/pre>\n
Output:<\/strong> In this code of Python, ‘San Francisco<\/strong>‘ in states_cities[‘California’]<\/strong> returns True<\/strong>, confirming that ‘San Francisco<\/strong>‘ is one of the major cities in California.<\/p>\n
True<\/code><\/pre>\n
\n
\"python<\/figure>\n<\/div>\n
Python Dictionary Contains Another Dictionary<\/h3>\n
In some scenarios, a Python dictionary contains another dictionary as its value. They are called nested dictionary in Python<\/strong>.<\/p>\n
For instance<\/strong>, Consider you are managing a database of U.S. states, with each state having a nested Python dictionary of additional information, and you need to check for a specific key in the nested dictionary.<\/p>\n
states_details = {\n    'California': {\n        'Capital': 'Sacramento',\n        'Population': 39538223,\n    },\n    'Texas': {\n        'Capital': 'Austin',\n        'Population': 29145505,\n    },\n}\n\nprint('Capital' in states_details['California'])<\/code><\/pre>\n
Output:<\/strong> In this case, ‘Capital<\/strong>‘ in states_details[‘California’]<\/strong> returns True<\/strong>, indicating that the nested dictionary contains the key ‘Capital<\/strong>‘.<\/p>\n
True<\/code><\/pre>\n
\n
\"python<\/figure>\n<\/div>\n
Python Dictionary Contains Duplicate Keys<\/h3>\n
A Python dictionary contains multiple keys<\/strong> but cannot have duplicate keys. Each key must be unique. If a duplicate key is found, the last occurrence will override the previous values.<\/p>\n
For example<\/strong>, In case you accidentally define a dictionary with duplicate keys, Python will retain the last occurrence.<\/p>\n
duplicate_keys = {\n    'a': 1,\n    'b': 2,\n    'a': 3,\n}\n\nprint(duplicate_keys)<\/code><\/pre>\n
Output: <\/strong>Here, even though the dictionary is defined with duplicate keys, the output is {‘a’: 3, ‘b’: 2}<\/strong>, retaining the last occurrence<\/strong> of ‘a<\/strong>‘.<\/p>\n
{'a': 3, 'b': 2}<\/code><\/pre>\n
\n
\"Python<\/figure>\n<\/div>\n
Python dictionary contains key value pair<\/h3>\n
For checking Python dictionary contains a key-value pair<\/strong>, utilize items() alongside the in keyword.<\/p>\n
For example<\/strong>, Let’s take a record of the participants and their selected subjects for the quiz and check for one of them with their selected subject,<\/p>\n
Name_with_subject = {'John': ['Math', 'Science'], 'Emily': ['English', 'History']}\nif ('John', ['Math', 'Science']) in Name_with_subject.items():\n    print(\"Yes\")<\/code><\/pre>\n
Output:<\/strong> Here, as the name is in the dictionary so, the if condition holds True<\/strong> and gives the desired output.<\/p>\n
Yes<\/code><\/pre>\n
\n
\"Python<\/figure>\n<\/div>\n
Methods to check what the Python Dictionary contains<\/h2>\n
There are many different methods to prevent if the Python Dictionary includes a key, values, or pair.<\/p>\n
\n\n\n\n\n\n\n\n\n\n\n
Name<\/th>\nDescription<\/th>\n<\/tr>\n<\/thead>\n
The in<\/strong> Keyword<\/td>\nThe in<\/strong> keyword in Python is used to check<\/strong> if a specified key exists within a dictionary.<\/td>\n<\/tr>\n
The get()<\/strong> Method<\/td>\nThe get()<\/strong> method in Python is used to retrieve the value for a specified key from the dictionary<\/strong>.<\/td>\n<\/tr>\n
The keys()<\/strong> Method<\/td>\nThe keys()<\/strong> method returns a view object that displays a list of all the keys in the dictionary.<\/strong><\/td>\n<\/tr>\n
The values() <\/strong>Method<\/td>\nThe values()<\/strong> method is used to check<\/strong> if a specific value exists in the dictionary.<\/td>\n<\/tr>\n
The items()<\/strong> Method<\/td>\nThe items()<\/strong> method returns a view object that displays a list of dictionary’s (key, value) tuple pairs<\/strong>.<\/td>\n<\/tr>\n
The all()<\/strong> Function<\/td>\nThe all()<\/strong> function returns True<\/strong> if all items in an iterable are true<\/strong>.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>
List of methods present in Python to check whether the dictionary has the specified key, value, or pair.<\/figcaption><\/figure>\n
Let’s see them one by one using demonstrative examples:<\/p>\n
Method 1: Using the in Keyword to Check for a Key<\/h3>\n
The in keyword in Python is used to check if a specified key exists within a dictionary. This method returns True if the key is found in the dictionary, and False otherwise. It is a fast and straightforward way to check for the existence of a key.<\/p>\n
Scenario:<\/strong> Checking if a state is in a dictionary of U.S. states and their populations.<\/p>\n
state_populations = {'California': 39538223, 'Texas': 29145505, 'Florida': 21538187}\n# Checking if 'Texas' is a key in the state_populations dictionary.\nif 'Texas' in state_populations:\n    print(f\"Texas has a population of {state_populations['Texas']}.\")<\/code><\/pre>\n
Output:<\/strong> In this case, ‘Texas<\/strong>‘ is found in the state_populations<\/strong> Python dictionary, and the population is printed out.<\/p>\n
Texas has a population of 29145505.<\/code><\/pre>\n
\n
\"Python<\/figure>\n<\/div>\n
Method 2: Using the get() Method to Check for a Key:<\/h3>\n
The get()<\/strong> method in Python is used to retrieve the value for a specified key from the dictionary. It returns None<\/strong> if the key does not exist (unless a default value is specified). By checking the returned value, we can determine whether a key exists in the dictionary in Python.<\/p>\n
Scenario:<\/strong> In a dictionary of national parks and their respective states, you want to find out in which state “Yosemite National Park<\/strong>” is located.<\/p>\n
national_parks = {'Yosemite': 'California', 'Grand Canyon': 'Arizona', 'Everglades': 'Florida'}\npark = national_parks.get('Yosemite')\nif park:\n    print(f\"Yosemite National Park is in {park}.\")\nelse:\n    print(\"This national park isn't in the dictionary.\")\n<\/code><\/pre>\n
Output:<\/strong> Here, the get() <\/strong>method returns California as ‘Yosemite<\/strong>‘ was in the national_park<\/strong> Python dictionary.<\/p>\n
Yosemite National Park is in California.<\/code><\/pre>\n
\n
\"python<\/figure>\n<\/div>\n
Method 3: Using the keys() Method to Check for a Key<\/h3>\n
The keys()<\/strong> method returns a view object that displays a list of all the keys in the dictionary. You can use the in keyword to check if a specific key exists within the keys.<\/p>\n
Scenario:<\/strong> You’re organizing a road trip and have a list of states you’ll visit. You want to confirm if “Nevada<\/strong>” is one of your destinations.<\/p>\n
road_trip_states = {'California': 'Los Angeles', 'Arizona': 'Phoenix', 'Utah': 'Salt Lake City'}\nif 'Nevada' in road_trip_states.keys():\n    print(\"Nevada is one of the destinations!\")\nelse:\n    print(\"Nevada isn't on the list.\")\n<\/code><\/pre>\n
Output:<\/strong> Here, the key()<\/strong> method returns False<\/strong> as ‘Nevada<\/strong>‘ is not in the road_trip_states<\/strong> dictionary in Python.<\/p>\n
Nevada isn't on the list.<\/code><\/pre>\n
\n
\"dictionary<\/figure>\n<\/div>\n
Method 4: Using the values() Method to Check for a Value<\/h3>\n
The values()<\/strong> method is used to check if a specific value exists in the dictionary. It returns a view object that displays a list of all the values in the dictionary Python. You can use the in keyword to check if a particular value is present among the values.<\/p>\n
Scenario:<\/strong> Within a Python dictionary of U.S. states and their famous foods, you want to see if any state is famous for “Burgers<\/strong>“.<\/p>\n
state_foods = {'New York': 'Pizza', 'Maine': 'Lobster', 'Texas': 'BBQ'}\nif 'Burgers' in state_foods.values():\n    print(\"One of the states is famous for Burgers!\")\nelse:\n    print(\"No state in the list is particularly famous for Burgers.\")\n<\/code><\/pre>\n
Output<\/strong>: In this example, the value()<\/strong> method returns False<\/strong> as ‘Burgers<\/strong>‘ is not in the state_foods<\/strong> dictionary in Python.<\/p>\n
No state in the list is particularly famous for Burgers.<\/code><\/pre>\n
\n
\"dictionary<\/figure>\n<\/div>\n
Method 5: Using the items() Method to Check for a Key-Value Pair<\/h3>\n
The items()<\/strong> method returns a view object that displays a list of dictionary’s (key, value) tuple pairs. You can use the in keyword to check if a particular key-value pair is present in the dictionary.<\/p>\n
Scenario:<\/strong> You have a dictionary of U.S. cities and their nicknames in Python. You want to confirm that Chicago is indeed called “The Windy City<\/strong>“.<\/p>\n
city_nicknames = {\n    'New York': 'The Big Apple',\n    'Los Angeles': 'City of Angels',\n    'Chicago': 'The Windy City'\n}\nif ('Chicago', 'The Windy City') in city_nicknames.items():\n    print(\"Yes, Chicago is called 'The Windy City'.\")\nelse:\n    print(\"This nickname doesn't match the city.\")<\/code><\/pre>\n
Output:<\/strong> In this example, the conditional statements return True<\/strong> as (‘Chicago’, ‘The Windy City’)<\/strong> is in the city_nicknames<\/strong> in dictionary Python.<\/p>\n
Yes, Chicago is called 'The Windy City'.<\/code><\/pre>\n
\n
\"contains<\/figure>\n<\/div>\n
Method 6: Using the all() Function to Check for Multiple Keys or Values<\/h3>\n
The all()<\/strong> function returns True<\/strong> if all items in an iterable are true. It can be used to check if multiple keys or values exist in a Python dictionary by iterating over each item and checking their existence.<\/p>\n
Scenario for Multiple Keys:<\/strong> You’re studying famous U.S. landmarks and have a list in your dictionary. You want to ensure that both “Statue of Liberty<\/strong>” and “Mount Rushmore<\/strong>” are on your list.<\/p>\n
landmarks = {\n    'Statue of Liberty': 'New York',\n    'Golden Gate Bridge': 'California',\n    'Mount Rushmore': 'South Dakota'\n}\nlandmarks_to_check = ['Statue of Liberty', 'Mount Rushmore']\nif all(landmark in landmarks for landmark in landmarks_to_check):\n    print(f\"All landmarks, {', '.join(landmarks_to_check)}, are in the list.\")<\/code><\/pre>\n
Output:<\/strong> Here, the all()<\/strong> function returns True<\/strong> as all keys present in the list.<\/p>\n
All landmarks, Statue of Liberty, Mount Rushmore, are in the list.<\/code><\/pre>\n
\n
\"contains<\/figure>\n<\/div>\n
Scenario for Multiple Values:<\/strong> In a dictionary of car manufacturers and their country of origin, you want to verify if the USA and Japan are both represented.<\/p>\n
car_manufacturers = {'Ford': 'USA', 'Toyota': 'Japan', 'BMW': 'Germany'}\ncountries_to_check = ['USA', 'Japan']\nif all(country in car_manufacturers.values() for country in countries_to_check):\n    print(f\"Both countries, {', '.join(countries_to_check)}, are present.\")<\/code><\/pre>\n
Output:<\/strong> Here, the all()<\/strong> function returns True<\/strong> as all values present in the list.<\/p>\n
Both countries, USA, Japan, are present.<\/code><\/pre>\n
\n
\"python<\/figure>\n<\/div>\n
Conclusion<\/h2>\n
In summary, understanding what the Python Dictionary contains<\/strong> means, like various elements such as keys, values, pairs of both, <\/strong>or other dictionaries<\/strong>, and how we can check what the dictionary contains in Python<\/strong> using different six methods like the ‘in<\/strong>‘ keyword, get() <\/strong>method, keys()<\/strong> method, values()<\/strong> method, items()<\/strong> method or all()<\/strong> method with illustrative examples.<\/p>\n
Recognizing the scenarios and applying the appropriate syntax to verify the existence of elements in a Python dictionary effectively can lead to error-free coding.<\/p>\n
You may also like to read:<\/p>\n