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Last updated: 11 Feb 2025
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A Python dictionary is used to store data in a key-value pair, and it can replicate a real-world arrangement that contains a value for a specified key. We can’t change its data structure, and it is defined using keys and values.
In a dictionary, a key is made of a single element, whereas a value can be of any data type, such as a tuple, list, integer, etc. Keys are immutable objects in Python.
Dictionary is one of the four built-in data structures in Python used to store data in key-value pairs. A key works as a unique identifier for an element and an attribute to locate the data in the memory. A value is the data related to that key. Values can be of any data type, but keys are immutable, so we can change them to only numbers, strings, or tuples.
Although dictionaries store information, such as definitions and words, they can be used for various other purposes. As dictionaries are mutable, we can’t change them once created. Also, they are unordered, which means the items in a dictionary are not stored in any specific order.
dict_var = {key1 : value1, key2 : value2, …..}
Key Points to Remember
Keys can be only a single element.
Keys are case-sensitive, so a name written in uppercase or lowercase is treated differently.
Creating a Python dictionary is as easy as placing the required key and value pairs inside curly braces. The elements are separated using commas. Out of the value pairs that a dictionary holds, one is key while the other is its key:value. The key, which must be immutable, is placed on the left side of the colon (:) and can be repeated.
The value, any data type, is on the right and can be duplicated. We use a comma to separate each key-value pair.
Please note that keys in a dictionary are case-sensitive. The same name written in different cases will be treated differently.
We use the built-in data type to create a dictionary, which stores all data types, such as strings, integers, and lists. The dictionary data type is the same as a list but uses keys rather than indexes to look up values.
When we use the dict() function to create a Python dictionary, it takes two arguments:
A list of keys
A list of values
Please Note
{} is used to place the required key and value pairs within.
: is used to separate key-value pairs.
, is used to separate multiple key-value pairs.
my_dic = {'key1' : 'value1', 'key2' : 'value2', .....,'key_n': 'value_n'}
address = {
"name" " Wscubetech",
"location1" : "jodhpur",
"location2" : "jaipur"
}Python dictionaries are mutable data structures, so we can store key-value pairs in them. Once we create a dictionary, we can add, remove, or update elements using different methods.
We can use the built-in update() method to update an existing value in a dictionary. It requires a key and a value as arguments, and the key must be assigned a value. We can also add nested key values to an existing dictionary.
When you add a value and the key value exists in the dictionary, the value is updated; otherwise, a new key value is added to the dictionary.
address = {
"name": " Wscubetech"
}
address['location1'] = "jaipur"
address.update({'location2' : 'jodhpur'})
print(address){'name': ' Wscubetech', 'location1': 'jaipur', 'location2': 'jodhpur'}
We can access an element or item of a dictionary by referring to its key name. A key can be used inside square brackets to access values in a dictionary. We also use square brackets for indexing and slicing Python strings.
address = {'name': ' Wscubetech', 'location1': 'jaipur', 'location2': 'jodhpur'}
print(address['name'])
print(address['location1'])
print(address['location2'])Wscubetech
jaipur
jodhpurWe can delete elements of a dictionary or the entire dictionary using the del keyword.
We also use the pop() method to remove an element. This method takes a key value as an argument and deletes the key-value pair from the dictionary. If the key doesn’t exist in the dictionary, the pop() method will raise an error.
The popitem() method is used to delete an arbitrary element from the dictionary. The method deletes a random key-value pair and returns it as a tuple. If the dictionary is empty, it will throw a KeyError.
address = {'name': ' Wscubetech', 'location1': 'jaipur', 'location2': 'jodhpur', 'course':'python'}
del address['name'] #remove name key
print(address)
address.pop('location2') #remove location2 key
print(address)
address.popitem() #remove last key-value pair
print(address){'location1': 'jaipur', 'location2': 'jodhpur', 'course': 'python'}
{'location1': 'jaipur', 'course': 'python'}
{'location1': 'jaipur'}In a Python dictionary, keys refer to unique identifiers used to access values, whereas values are data related to those keys.
A dictionary is unordered and mutable that stores Python objects as values. We use it to store key-value pairs.
all() is used to check if all values in a dictionary are True.
any() assesses if a value in a dictionary is True.
cmp() compares two dictionaries, but this method is not available in Python 3.
sorted() returns a new sorted list of keys in a dictionary
We use print() to display all contents of a dictionary. We access keys or values to print the complete dictionary or specific elements.
We declare a dictionary in Python by using key-value pairs enclosed within curly braces {}.
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