Question 1

Question 1Why are dictionaries called mutable types?

Accepted Answer

Dictionaries can be changed by adding new key-value pairs and by deleting or changing the existing ones. Hence they are called as mutable types.For example:d = {"a" : 1 , "b" : 2}
d["c"] = 3 
d["b"] = 4
del d["a"]
print(d)Output{'b': 4, 'c': 3} 
dict["c"] = 3 adds a new key-value pair to dict.dict["b"] = 4 changes existing key-value pair in dict.del dict["a"] removes the key-value pair "a" : 1

Question 2

Question 2What are different ways of creating dictionaries?

Accepted Answer

The different ways of creating dictionaries in Python are:1. By using curly brackets and separating key-value pairs with commas as per the syntax below: = {:, :...} For example: d = {'a': 1, 'b': 2, 'c': 3} 2. By using dictionary constructor dict(). There are multiple ways to provide keys and values to dict() constructor:i. Specifying key:value pairs as keyword arguments to dict() function:For example:Employee = dict(name = 'john' , salary = 1000, age = 24) print(Employee)Output{'name': 'john', 'salary': 1000, 'age': 24} ii. Specifying comma separated key:value pairs:Key:value pairs are enclosed in curly braces in this format.For example:Employee = dict({'name': 'john', 'salary': 1000, 'age': 24})Output{'name': 'john', 'salary': 1000, 'age': 24} iii. Specifying keys and its corresponding values separately:Keys and Values are enclosed separately in parentheses and are given as arguments to zip() function.For example:Employee = dict(zip(('name','salary','age'),('John',10000,24))) Output{'name': 'John', 'salary': 10000, 'age': 24} iv. Specifying key:value pairs separately in form of sequences:One list or tuple that contains lists/tuples of individual key:value pairs is passed as an argument to dict().For example:Employee = dict([['name','John'],['salary',10000],['age',24]]) print(Employee)Output{'name': 'John', 'salary': 10000, 'age': 24} 3. By using fromkeys() function:fromkeys() function is used to create a new dictionary from a sequence containing all the keys and a common value, which will be assigned to all the keys.For example:x = ('list', 'set', 'dictionary') y = 'mutable' my_dict = dict.fromkeys(x, y) print(my_dict)Output{'list': 'mutable', 'set': 'mutable', 'dictionary': 'mutable'}

Question 3

Question 3What values can we have in a dictionary?

Accepted Answer

A dictionary can have values of all data types i.e., integers, floats, strings, booleans, sequences and collections, etc. For example:d = {1:'a' , 2: 2 , 3: True , 4: 3.5 , 5: "python",(1,2,3) : 4}

Question 4

Question 4How are individual elements of dictionaries accessed?

Accepted Answer

Individual elements of a dictionary can be accessed by using their corresponding keys as per the syntax shown below: []For example:d = {'a': 1, 'b': 2, 'c': 3} print(d['a'])Output1 In addition to this, we can also use the get( ) method to get value of the given key as per the syntax shown below:.get(, [default])For example:d = {'a': 1, 'b': 2, 'c': 3} print(d.get('a'))Output1

Question 5

Question 5How is indexing of a dictionary different from that of a list or a string?

Accepted Answer

In lists or strings, the elements are accessed through their index where as in dictionaries, the elements are accessed through the keys defined in the key:value pairs. Moreover, lists and strings are ordered set of elements but dictionaries are unordered set of elements so its elements cannot be accessed as per specific order.

Question 6

Question 6Which of the following types qualify to be the keys of a dictionary?StringtupleIntegerfloatlistdictionary

Accepted Answer

The following types can be used as keys of a dictionary because they are immutable:StringtupleIntegerfloatAs lists and dictionaries are mutable so they cannot be used as keys of a dictionary.

Question 7

Question 7Can you change an element of a sequence or collection? What if a collection is a dictionary? What if a sequence is a string?

Accepted Answer

Elements of a collection or sequence can be changed only if the collection or sequence is mutable. Hence, for dictionaries, the elements can be changed as dictionaries are mutable but for strings is cannot be changed as strings are immutable.Example:>>> d = {1 : 'a', 2: 'b'}
>>> d[1] = 'c'
>>> str = "hello"
>>> str[1] = "python"Output{1: 'c', 2: 'b'}
TypeError: 'str' object does not support item assignment

Question 8

Question 8What do you understand by ordered collection and unordered collection ? Give examples.

Accepted Answer

Ordered Collection is the one in which the position of each element is fixed.Example: List, strings, TuplesUnordered Collection is the one in which position of each element is not fixed i.e., the order of all the elements are not maintained.Example: Sets, Dictionaries

Question 9

Question 9How do you add key:value pairs to an existing dictionary?

Accepted Answer

There are three ways by which new key:value pairs can be added to an existing dictionary:1. By using assignment as per the following syntax:[] = For example:d = {1 : 'a' , 2 : 'b'} d[3] = 'c' print(d)Output{1: 'a', 2: 'b', 3: 'c'}2. By using update() method:update() method merges key:value pairs from new dictionary into the original dictionary adding or replacing as needed. The syntax to use this method is:.update() For example:d = {1 : 'a' , 2 : 'b'} d.update({3 : 'c'}) print(d)Output{1: 'a', 2: 'b', 3: 'c'}3. Using setdefault() method:It inserts a new key:value pair only if the key doesn't already exist. If the key already exists, it returns the current value of the key. The syntax to use this method is:.setdefault(,) For example:d = {1 : 'a' , 2 : 'b'} d.setdefault(3,'c') print(d)Output{1: 'a', 2: 'b', 3: 'c'}

Question 10

Question 10Can you remove key:value pairs from a dictionary and if so, how?

Accepted Answer

Yes, key:value pairs can be removed from a dictionary. The different methods to remove key:value pairs are given below:1. By using del command:It is used to delete an item with the specified key name. The syntax for doing so is as given below:del []For example:dict = {'list': 'mutable', 'tuple': 'immutable', 'dictionary': 'mutable'} del dict["tuple"] print(dict)Output{'list': 'mutable', 'dictionary': 'mutable'} 2. By using pop() method:This method removes and returns the dicitionary element associated to the passed key. It is used as per the syntax:.pop(key, )For example:dict = {'list': 'mutable', 'tuple': 'immutable', 'dictionary': 'mutable'} dict.pop("tuple") print(dict)Output{'list': 'mutable', 'dictionary': 'mutable'} 3. popitem() method:This method removes and returns the last inserted item in the dictionary. It is used as per the syntax:.popitem()For example:dict = {'list': 'mutable', 'tuple': 'immutable', 'dictionary': 'mutable'} dict.popitem() print(dict)Output{'list': 'mutable', 'tuple': 'immutable'} Here, the last element of dict was 'dictionary': 'mutable' which gets removed by function popitem().

Question 11

Question 1The keys of a dictionary must be of immutable	types.

Accepted Answer