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How to create a dictionary in Python?

How to create a dictionary in python

Dictionary is a data structure in Python that represents our data in the form of keys and values.

Each value in a dictionary can be accessed using its corresponding key.

Let us have a look at some more properties of a Dictionary-

  1. All the keys in a dictionary should be unique.
  2. The keys in the dictionary are case-sensitive which means 'shape' and 'SHAPE' are treated as two different keys.

Let us have a look that how we can create a dictionary in Python-

Syntax of Dictionary

a={'Fruit_name':'Apple','Color':'Red','Shape':'Spherical'}

Now let’s see after creating it how we can verify this data structure.

The following program illustrates how we can check the type-

 #using dictionary
 a={'Fruit_name':'Apple','Color':'Red','Shape':'Spherical'}
 print(a)
 print(type(a)) 

INPUT-

OUTPUT-

In the output, we can observe the dictionary ‘a’ is printed that contains three keys and type() returns its datatype.

The next thing that we will discuss in this article is how we can access the values in our dictionary.

Accessing values in a dictionary

In the following program, we have used the keys to access the values of our dictionary.

 #using dictionary
 a={'Fruit_name':'Apple','Color':'Red','Shape':'Spherical'}
 print(a)
 print(type(a))
 #accessing elements using keys
 print(a['Fruit_name'])
 print(a['Color'])
 print(a['Shape']) 

INPUT-

OUTPUT-

In the output, we can observe the following things-

  1. The dictionary ‘a’ is printed.
  2. The data type is returned which is <class ‘dict’>.
  3. Then the three values are displayed when we access them using the keys 'Fruit-Name', 'Color', and 'Shape'.

Now, let us see what are the different ways of creating a dictionary in Python.

WAYS TO CREATE A DICTIONARY

Here, we will try to understand this with the help of four methods-

  1. Simple creation of a list
  2. Using dict()
  3. Using {}
  4. Using defaultdict

In the first method, we can see a dictionary is created using the most basic approach where we have specified our keys and values in the curly braces.

Following program illustrates the same.

 #creating a dictionary
 a={'Fruit_name':'Apple','Color':'Red','Shape':'Spherical'}
 print(a)
 print("The type of a is {}".format(type(a))) 

INPUT-

OUTPUT-

On executing the given program, the expected results are displayed.

The second method that we will discuss here is creating a dictionary using dict().

So, here we have declared object a as dict() and then defined our dictionary.

Following program illustrates the same-

 #creating a dictionary
 a=dict()
 a={'Fruit_name':'Apple','Color':'Red','Shape':'Spherical'}
 print(a)
 print("The type of a is {}".format(type(a))) 

INPUT-

OUTPUT-

On executing the code, the expected results are displayed.

The third method that we will discuss is creating a dictionary by declaring a as {} and then defining the value for each key.

Then we have printed a and its data type.

Following program illustrates the same-

 #creating a dictionary
 a={}
 a["Fruit_Name"]="Apple"
 a["Color"]="Red"
 a["Shape"]="Spherical"
 print(a)
 print("The type of a is {}".format(type(a))) 

INPUT-

OUTPUT-

The last method that we will discuss is creating a dictionary using defaultdict().

Here we have provided a list that contains the key, value pairs and then applied the method defaultdict() to it and then added each value corresponding to the key, and then printed it.

Following program illustrates the same-

 #using defaultdict
 from collections import defaultdict
 lst=[('Fruit_Name','Apple'),('Color','Red'),('Shape','Spherical'),('Fruit_Name','Grapes')]
 dict_fruits=defaultdict(list)
 for key,value in lst:
     dict_fruits[key].append(value)
 print(dict_fruits) 

INPUT-

OUTPUT-

In the output, we can observe that first of all it tells us that it belongs to the <class 'list'> which is followed by a dictionary that has the keys and all the values are in the form of lists.

The next thing we will discuss in this article is how we add and modify the values in our dictionary.

Updating dictionary

Let us first see how we can add an element in the dictionary.

Following program illustrates the same-

 #adding an element in dictionary
 a={'Fruit_Name':'Apple','Color':'Red','Shape':'Spherical'}
 print(a)
 print("The type of a is {}".format(type(a)))
 a['Fruit_Name1']='Grapes'
 print(a) 

INPUT-

OUTPUT-

In the output, we can observe the new key-value pair being added.

Next, we will see how we can modify the value of a particular key.

Following program illustrates the same-

 #modifying an element in dictionary
 a={'Fruit_Name':'Apple','Color':'Red','Shape':'Spherical'}
 print(a)
 print("The type of a is {}".format(type(a)))
 a['Color']='Green'
 print(a) 

INPUT-

OUTPUT-

In the output, we can observe the value of color has been modified from ‘Red’ to ‘Green’.

In the last section of this article, we will take a brief idea of the methods that are used in a dictionary.

Methods used in Dictionary

  1. len() – The len() method returns the length of our dictionary. In the output, we can see that it comes out to be 3.
 #methods on dictionary
 a={'Fruit_Name':'Apple','Color':'Red','Shape':'Spherical'}
 print(len(a)) 
  • Dict.get(‘key’)-In this ‘Dict’ refers to the name of the dictionary and ‘key’ refers to the name of the key whose value we would like to fetch. We can see in the example it returns ‘Red’ when we provide the key ‘Color’.
 #methods on dictionary
 a={'Fruit_Name':'Apple','Color':'Red','Shape':'Spherical'}
 print(a.get('Color')) 
  • Dict.items()-In this method, ‘Dict’ refers to the name of the dictionary and it returns all the key-value pairs present in the dictionary.
 #methods on dictionary
 a={'Fruit_Name':'Apple','Color':'Red','Shape':'Spherical'}
 print(a.items()) 
  • Dict.keys()-In this method, 'Dict' refers to the name of the dictionary and it returns all the keys present in the dictionary. In the output, we can see it returns the keys 'Fruit_Name', 'Color', and 'Shape'.
 #methods on dictionary
 a={'Fruit_Name':'Apple','Color':'Red','Shape':'Spherical'}
 print(a.keys()) 
  • Dict.values()-In this method, ‘Dict’ refers to the name of the dictionary and it returns all the values present in the dictionary. In the output, we can see it returns the values ‘Apple’,’Red’ and ‘Spherical’.
 #methods on dictionary
 a={'Fruit_Name':'Apple','Color':'Red','Shape':'Spherical'}
 print(a.values()) 

So, in this article, we discussed dictionaries, how we can access them, how we can create them, and what are the different methods that we can apply to them.



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