Dictionary in Python

The dictionary is one of the datatypes used in Python for storing a collection of data values.

It is an unordered collection of elements where each element is stored as key-value pairs. It is also referred to as a mapping between a key and a value

Some Important features:

• Keys should be unique in the dictionary while values can be similar
• Each key is separated from its value by a comma(:),and every element is separated by commas, and the entire dictionary is enclosed in curly braces
• The values can be of any type, while keys should be of strings, numbers, or tuple type
• Dictionary is immutable, which means we can add, update or delete the existing element in the string

Example:

{"tutorial":"Dictionaries"}

Creating Dictionary

Dictionary can be created by simply enclosing key-value pairs inside curly braces {}, separated by a comma. The colon (:) is used to separate the key and the value in a pair



here {} represent empty dictionary

It can also be created using dict() method, by passing the comma-separated key: value pairs inside the dict() method

Accessing Dictionary

To access a value from dictionary,you have to use square brackets along with the key to obtain its value

Example:

If we try to access that key which does not exist in the dictionary,it will throw error as:

You can also access the value by get() method.This method will return the value of given key from a dictionary

Traversing Dictionary

In python, we can easily access each element of a dictionary by using a for loop

Example:

Appending values in the dictionary

As dictionaries are immutable, we can add new elements to existing dictionaries, extend them with single pairs, or combine two of them into one

Syntax:
Dictionary_name[key_name]=value

Example:

Updating values in the dictionary

We can also update the dictionary by changing key-value pairs or by combining another dictionary with an existing one

Syntax:
Dictionary_name[key_name]=value

Example:



We can also update the existing pairs in the dictionary,and can merge the keys and values of one dictionary with another and if same key is there then it overwrites it value,all this is done by update()method

Deleting element in the dictionary

To remove an element from the existing dictionary, we can use the pop() method and the del command.

We can use these methods ,to delete the single element or the last element or delete the entire dictionary only.

The following methods are:

Del command

This command is used to delete an element from a dictionary. The format to delete an element from a dictionary by using del is:

Del dictionary_name[key_name]

No value is returned when using the del method

Example:



We can also delete the entire dictionary by using del keyword followed by dictionary name

Del dictionary_name

Using pop() method

This method is also used to delete an element from a dictionary. The format to delete an element from a dictionary by using the pop() method is:

Dictionary_name.pop(key_name)

This method will not only delete the element from the existing dictionary but also return the deleted element

Membership Operators

In python, we can also check whether a particular key exists in the given dictionary or not using membership operators. These operators are ‘in’ and ‘not in’

‘in’ operator: This operator returns true or false depending on whether the given key exists in a dictionary

'not in’ operator. This operator returns true when that given key does not exist in the dictionary

Example:

Basic Dictionary functions

Method	Description
len()	returns number of elements in the dictionary
clear()	Removes all key-value pairs in the dictionary
get()	Returns the value for the specified key
items()	returns each element in a dictionary as a tuple in a list
keys()	Returns all the keys of the dictionary
values()	Returns all the list of values in the dictionary
copy()	Creates copy of the dictionary
popItem()	Deletes last element of the dictionary
setDefault()	Returns the value of the specified key
max() and min()	Returns maximum and minimum value of the dictionary
Sorted()	Sorts the element in the dictionary

len()

This method is used to return number of key-value pairs in the dictionary

Syntax:
len(d)
d is a dictionary

For Example:

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clear()

This method is to remove all key-value pairs in the dictionary

Syntax:
d.clear()
d is a dictionary

Example:

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get()

This method is used to provide value for the given key.If that given key is not available ,then it returns default value as None

Syntax:
Dict_name.get(key,default =None)
Key-This is the key to be searched in the dictionary
Default-This is the value to be returned when that given key is not found in the dictionary

Example:

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Items()

This method returns all the items of dictionary as a list of tuple having key-value pairs

Syntax:
d.items()
d is a dictionary

Example:

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keys()

This method returns all the list of keys in a dictionary

Syntax:
d.keys()
d is a dictionary

Example:

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Values()

This method returns all the list of values from key-value pairs in a dictionary

Syntax:
d.values()
d is a dictionary

Example:

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copy()

This method is used to create copy of the dictionary

Syntax:
d.copy()
d is a dictionary

Example:

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popItem()

This method is used to delete last element from dictionary and returns that deleted element

Syntax:
d.popitem()
d is a dictionary

Example:

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setDefault()

This method returns the value of the given key.If the key does not exist ,it inserts the key with the default value

This method returns:

• Value of the key,when it is in dictionary
• None,if key is not in the dictionary and default value is not specified
• Default_value,if the key is not in the dictionary and default value is specified

Example:

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max() and min()

This max() methods returns key with the maximum value in the dictionary

And min() method returns key with the minimum value in the dictionary

Syntax:
Dictionary.max()
Dictionary.min()

Example:

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sorted()

This method is used to sort the elements in the dictionary by its key or values

Syntax:
d.sorted()
d is the dictionary

Example:

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