Python Dictionary

Dictionary is that collection data type of Python which is unordered , changeable and indexed and these are also written by curly brackets {} , having keys and its values .
Examples:-

Create a dictionary

Try it yourself

Output of this Program

So here in above program we had given the command of creating dictionary data to our Python interpreter. Let’s see .

So our ‘Dictionary’ is been ready.

Access Items in dictionary

Here in the Dictionary data type ,we can access keys in dictionary by referring to the key value inside square bracket[] .

Let’s understand this by an example :-

Try it yourself

Output of this Program

So here in the above program we just want to access the value ‘Carrot’ which is the value of ‘Vegetable’ . So we just type down the ‘Vegetable’ key to access ‘Carrot’ .
So let’s see what output it gives :-

So we just get the ‘Carrot’ value which we want just by passing the key.

Change dictionary values

We can change the dictionary items just by referencing the keys and giving it the desired value.
Let’s understand this by the following example :-

Try it yourself

Output of this Program

So here in the above Program we just gave command to our Python interpreter that we want to change the value of ‘Fruits’ from ‘Apple’ to ‘Banana’ .
So let’s see what output it gives :-

So here it just changes the ‘Apple’ to ‘Banana’

Loops through dictionary

Unlike other collection data type here also loops is done by using ‘for’ loop but only the keys values we can get in return , although there are methods too how we can get the values in return .

Let’s understand this by an example :-

Try it yourself

Output of this Program

So this is the method basically to give command to our Python interpreter that we want to print all the keys , one by one .
So let’s see what output it gives :-

Here we get all the keys present in our program , but if we want to get values in return than there is a different way

Let’s understand this by an example :-

Try it yourself

Output of this Program

So this is the method basically to give command to our Python interpreter that we want to print all the values , one by one .
So let’s see what output it gives :-

So here we get the values in return.

( More about Loops we will talk further on the looping section. )

Check if Key exist in dictionary

We can also check keys in our dictionary by using the ‘in’ keyword.
Let us understand this by the following example :-

Try it yourself

Output of this Program

So our ‘Fruits’ is in the dictionary and it gives us the correct output.

( We will read in detail regarding ‘if’ statement . )

Methods in Dictionary

As we know that methods are basically the function which we want to perform in our coding . In Python there are some inbuilt methods are there for dictionary too.
So let’s see some of them :-

The len() method - The len() method - It just returns the length of the Dictionary , considering key and its value as one .

Try it yourself

Output of this Program

So here we just get the length of the set based on their index number.

Adding items on dictionary

Adding an element in dictionary we have to use new index key and assigning it a value.
Let’s understand this by the example :-

Try it yourself

Output of this Program

So here through add() method we add new keys to our dictionary.

Removing item of dictionary

There are several types of method to removing the dictionary:-

• pop() method
• popitem() method
• del() method
• clear() method

the pop method remove any item or key with the specified key name.
example:-

Try it yourself

Output of this Program

Here we had just removed the ‘Fruits’ key plus its value too from our dictionary by pop() method.

the popitem() method removes the last element or key of our dictionary.
example:-

Try it yourself

Output of this Program

So here our last key and its value is vanish just by using popitem() method .

the del() keyword removes the item specified key name.
example:-

Try it yourself

Output of this Program

So here we just deleted the key ‘Fruits’ and it value too.

del() keyword removes the whole dictionary too.
example:-

Try it yourself

Output of this Program

So here we just deleted the whole dictionary.

clear () keyword empties the dictionary.
example:-

Try it yourself


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Output of this Program

Here whole dictionary is empty or invisible by using clear() method.

Copy a dictionary

We can copy the dictionary by giving references , and there are two methods of copying the dictionary.

• copy ()
• dict()

copy the dictionary through copy () methods .
example:-

Try it yourself

Output of this Program

Here we have copied thisdict keys and values into mydict, and when we print mydict , it give us all the elements which are present in thisdict

copy the dictionary through dict() methods .
example:-

Try it yourself

Output of this Program

So through dict() method we copied our thisdict library to mydict.

The dict() constructor , dict() can used to make new dictionary.

Try it yourself

Output of this Program

So here through set() constructor our set is ready.

Some methods of dictionary and their functionality

Python has set of built-in method that you can use the dictionary

Method	Description
clear()	Remove all element to dictionary
copy()	Return copy on the dictionary
fromkeys()	Create dictionary from given sequence
get()	Return values of the keys
items()	Returns view list of dictionary (key.values) pair
key()	Return the containing keys list of dictionary
pops()	Remove the element with specified keys
popitem ()	Remove the last inserted key-value pair
setdefault()	Insert key with values if key not present
update()	Updates the dictionary
values()	Returns all view values in dictionary

Check all these methods for good practice.