Tuples, Sets and Dictionaries Reading Material

 

1. What is a Tuple?

A tuple holds an ordered collection of items. A tuple is an immutable object, i.e. we cannot change the items of the tuple.

Creating a Tuple

• Created by enclosing elements within (round) brackets.
• Each item is separated by a comma.

Code

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a = 2

tuple_a = (5, "Six", a, 8.2)

print(type(tuple_a))

print(tuple_a)

PYTHON

Output

<class 'tuple'>

(5, 'Six', 2, 8.2)

Tuple with a Single Item

Code

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a = (1,)

print(type(a))

print(a)

PYTHON

Output

<class 'tuple'>

(1,)

Accessing Tuple Elements

Accessing

tuple

elements is also similar to string and list accessing.

Code

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a = 2

tuple_a = (5, "Six", a, 8.2)

print(tuple_a[1])

PYTHON

Output

Six

2. Are Tuples mutable?

No, Tuples are immutable. They cannot be modified.

Code

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tuple_a = (1, 2, 3, 5)

tuple_a[3] = 4

print(tuple_a)

PYTHON

Output

TypeError: 'tuple' object does not support item assignment

3. How to Unpack a tuple?

The values of any sequence can be directly assigned to variables. The number of variables on the left should match the length of the sequence.

Code

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tuple_a = ('R', 'e', 'd')

(s_1, s_2, s_3) = tuple_a

print(s_1)

print(s_2)

print(s_3)

PYTHON

Output

R

e

d

4. What is the difference between List and Tuple?

Basis for comparison	List	Tuple
Type	Lists are mutable	Tuples are immutable
Time Consumption	The list iteration is much slower compared to the tuple	The tuple iteration is much faster compared to the list
Appropriate Usage	It is very helpful in the case of deletion and insertion operations	It is comparatively helpful in the case of read-only operations, such as accessing elements

5. What are Sets?

Sets are the unordered collection of items.

Every set element is

• Unique (no duplicates)
• Must be immutable

Creating a Set

• Created by enclosing elements within {curly} brackets.
• Each item is separated by a comma.

Code

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a = 2

set_a = {5, "Six", a, 8.2}

print(type(set_a))

print(set_a)

PYTHON

Output

<class 'set'>

{8.2, 2, 'Six', 5}

Set items need not be in the same order as defined.

No Duplicate Items

Sets contain unique elements

Code

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set_a = {"a", "b", "c", "a"}

print(set_a)

PYTHON

Output

{'b', 'a', 'c'}

6. What is a Dictionary?

A Dictionary is an unordered collection of items. Every dictionary item is a Key-Value pair.

7. How to create a Dictionary?

A dictionary is created by enclosing items within {curly} brackets.

Each item in the dictionary has a Key-Value pair separated by a comma.

Code

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dict_a = {

"name": "Teja",

"age": 15

}

PYTHON

In the above dictionary, the

• keys
   are 
  name
   and 
  age
• values
   are 
  Teja
   and 
  15

8. How to get the keys of a dictionary?

The keys() method allows us to get the keys of dictionary. It returns a view object of the type

dict_keys

that holds a list of all keys.

Code

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dict_a = {

"name": "Teja",

"age": 15

}

print(dict_a.keys())

PYTHON

Output

dict_keys(['name', 'age'])

9. Why List can't be used as a key in the dictionary/ Are the dictionary keys mutable?

A Python dictionary can have only keys of immutable types. Lists cannot be used as keys in a dictionary because they are mutable.

10. How to create an empty dictionary?

Using 

dict()

 built-in function

code

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dict_a = dict()

print(type(dict_a))

print(dict_a)

PYTHON

Output

<class 'dict'>

{}

Using 

{ }

 symbol

code

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dict_a = {}

print(type(dict_a))

print(dict_a)

PYTHON

Output

<class 'dict'>

{}

11. How to combine two dictionaries?

We can combine two dictionaries using

update()

method:

Syntax

dictionary.update(iterable)

code

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dict_1 = {'a': 1, 'b': 2}

dict_2 = {'c': 3, 'd': 4}

dict_1.update(dict_2)

print(dict_1)

PYTHON

Output

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

12. What are the differences between Lists, Tuples, Sets and Dictionaries?

Lists	Tuples	Sets	Dictionaries
A list is an ordered collection of data	A tuple is an ordered collection of data	A set is an unordered collection	A dictionary is an unordered collection of data that stores data in Key-Value pairs
Lists are mutable	Tuples are immutable	Sets are mutable	Dictionaries are mutable
Lists are enclosed within square braces []	Tuples are enclosed within parenthesis ()	Sets are enclosed within curly brackets {}	Dictionaries are enclosed within curly brackets {}  in the form of Key-Value pairs
Example: [1, 2, 3, 4, 5]	Example: (1, 2, 3, 4, 5)	Example: {1, 2, 3, 4, 5}	Example: { a:1, b:2, c:3, d:4, e:5}
List allows duplicate elements	Tuple allows duplicate elements	Set will not allow duplicate elements	Dictionary doesn’t allow duplicate keys
List can be created using  list()  function	Tuple can be created using  tuple()  function	Set can be created using  set()  function	Dictionary can be created using  dict()  function