Top Interview Questions on Dictionary in Python

Three different ways of creating a Dictionary are:

1. Create an empty Dictionary

Dictionary1 = {}
print(Dictionary1)

Output:

{}

key1 = 'a'
value1 = 1
Dictionary1[key1] = value1

{'a': 1}

Dictionary1 = dict({1: 'a', 2: 'b'})
print(Dictionary1)

Output:

{1: 'a', 2: 'b'}

3. Create Dictionary with each item as Pair

Dictionary1 = dict([(1,'a'), (2, 'b')])
print(Dictionary1)

Output:

{1: 'a', 2: 'b'}

4. Creating Dictionary directly

Dictionary1 = {1: 'a', 2: 'b'}

Output:

{1: 'a', 2: 'b'}

Question 4: What is a Nested Dictionary? How is it created?

A dictionary inside the dictionary is known as a “Nested Dictionary”. For ex-

dictionary1 = {1: {'roll': '101', 'name': 'sam'},
                          2: {'roll': '102', 'name': 'ram'}}
print(dictionary1)

Output

{1: {'roll': '101', 'name': 'sam'}, 2: {'roll': '102', 'name': 'ram'}}

The elements of nested dictionary can be accessed using

print(dictionary[1]['roll'])

Output:

101

Elements in a Dictionary can be added in multiple ways:

1. Adding one pair at a time

Dict1 ={}
Dict1[0] = 'a'
Dict1[1] = 'b'
print("Dictionary after adding 3 elements: ", Dict1)

Output:

{0: 'a', 1: 'b' }

2. Adding more than one value to a single key

Dict1['values'] = 4, 5, 6
print("Dictionary after adding multiple values to a key: ", Dict1)

Output:

{0: 'a', 1: 'b', 'values': (4, 5, 6) }

3. Adding nested key-value pair

Dict1['Nested'] = {1: 'Analytics', 2: 'Life'}

Output:

{0: 'a', 1: 'b', 'values': (4, 5, 6), 'Nested': {1: 'Analytics', 2: 'Life'} }

Various methods used with Dictionary are:

1. clear()

It is used to delete all elements from a dictionary i.e., to create empty dictionary.

dict2 = {1: 'Analytics', 2: 'Vidhya'}
dict2.clear()
print(dict2)

Output:

{ }

It is used to get the value of the specified key.

x = dict2.get(2)
print(x)

Output:

Vidhya

3. copy()

It is used to return copy of a dictionary

dict3 = dict2.copy()
print(dict3)

Output:

{1: 'Analytics', 2: 'Vidhya'}

4. items()

It is used to return a list tuples consisting of key-value pairs.

Dict1 = {1: 'Analytics', 2: 'Vidhya'}
print(Dict1.items())

Output:

dict_items([(1, 'Analytics'), (2, 'Vidhya')])

5. keys() and values()

Returns all keys and values within a dictionary respectively.

Dict1.key()
Dict1.values()

Output:

dict_keys([1, 2]) 
dict_values(['Analytics', 'Vidhya'])

6. update()

This method updated value of a key in dictionary

Dict1.update({2:"Blogathon"})
print(Dict1)

Output:

{1: 'Analytics', 2: 'Blogathon'}

Here, zip() function takes iterables (it can be more than two also) and combines them in a tuple.

Output:

{1: 'a', 2: 'b', 3: 'c'}

The list of tuples can be created in following way:

dict1 = { 1: 'a', 2: 'b', 3: 'c' }
lst1 = list(dict1.items())
print(lst1)

Output:

[(1, 'a'), (2, 'b'), (3, 'c')]

A list can be created using the below code:

x = list(dict1.keys())
y = list(dict1.values())
for i in y:
      x.append(i)
print(x)

Output:

[1, 2, 3, 'a', 'b', 'c']

Key-value pair can be deleted by using ‘del’ keyword as shown below:

del dict1[1]
print(dict1)

Output:

{2: 'b', 3: 'c' }

The term ‘Mutable’ means we can add, remove or update key-value pairs in a dictionary.

Yes, the dictionary is mutable. For instance,

Dict1 = {1: 'a', 2: 'b', 3: 'c', 4: 'd' }
Dict1[2] = 'h'
print(Dict2)

Output:

{1: 'a', 2: 'h', 3: 'c', 4: 'd' }

Let’s define these two lists as list1 and list2 as follows:

list1 = [1, 2, 3, 4, 5]
list2 = ['a', 'b', 'c', 'd', 'e']
dict1 = {}
for i, j in zip(list1, list2):
    dict1[i] = j
print(dict1)

Output:

{1: 'a', 2: 'b', 3: 'c', 4: 'd', 5: 'e'}

Another way of achieving the same output:

dict1 = {i:h for i,j in zip(list1, list2)}
print(dict1)

Output:

{1: 'a', 2: 'b', 3: 'c', 4: 'd', 5: 'e'}

Below is the code to sort dictionaries using the key:

dict1 = {2: 'Apple', 1:'Mango', 3:'Orange', 4:'Banana'}
print(sorted(dict1.keys()))
for key in sorted(dict1):
      print("Sorted dictionary using key:",(key, color_dict[key]))

Output:

[1, 2, 3, 4] 
1: Mango
2: Apple
3: Orange
4: Banana