Namedtuple in Python

Python supports a type of container dictionaries called “namedtuple()” present in the module, “collections“. Like dictionaries, they contain keys that are hashed to a particular value. But on contrary, it supports both access from key-value and iteration, the functionality that dictionaries lack.

Example:

Python3

# Python code to demonstrate namedtuple()

from collections import namedtuple

# Declaring namedtuple()
Student = namedtuple('Student', ['name', 'age', 'DOB'])

# Adding values
S = Student('Nandini', '19', '2541997')

# Access using index
print("The Student age using index is : ", end="")
print(S[1])

# Access using name
print("The Student name using keyname is : ", end="")
print(S.name)

Output:

The Student age using index is : 19
The Student name using keyname is : Nandini

Let’s see various Operations on namedtuple() 

Access Operations

• Access by index: The attribute values of namedtuple() are ordered and can be accessed using the index number unlike dictionaries which are not accessible by index.
• Access by keyname: Access by keyname is also allowed as in dictionaries.
• using getattr(): This is yet another way to access the value by giving namedtuple and key value as its argument.

Python3

# Python code to demonstrate namedtuple() and
# Access by name, index and getattr()

# importing "collections" for namedtuple()
import collections

# Declaring namedtuple()
Student = collections.namedtuple('Student', ['name', 'age', 'DOB'])

# Adding values
S = Student('Nandini', '19', '2541997')

# Access using index
print("The Student age using index is : ", end="")
print(S[1])

# Access using name
print("The Student name using keyname is : ", end="")
print(S.name)

# Access using getattr()
print("The Student DOB using getattr() is : ", end="")
print(getattr(S, 'DOB'))

Output :

The Student age using index is : 19
The Student name using keyname is : Nandini
The Student DOB using getattr() is : 2541997

Conversion Operations

• _make() :- This function is used to return a namedtuple() from the iterable passed as argument.
• _asdict() :- This function returns the OrderedDict() as constructed from the mapped values of namedtuple().
• using “**” (double star) operator :- This function is used to convert a dictionary into the namedtuple().

Python3

# Python code to demonstrate namedtuple() and
# _make(), _asdict() and "**" operator

# importing "collections" for namedtuple()
import collections

# Declaring namedtuple()
Student = collections.namedtuple('Student',
                                 ['name', 'age', 'DOB'])

# Adding values
S = Student('Nandini', '19', '2541997')

# initializing iterable
li = ['Manjeet', '19', '411997']

# initializing dict
di = {'name': "Nikhil", 'age': 19, 'DOB': '1391997'}

# using _make() to return namedtuple()
print("The namedtuple instance using iterable is  : ")
print(Student._make(li))

# using _asdict() to return an OrderedDict()
print("The OrderedDict instance using namedtuple is  : ")
print(S._asdict())

# using ** operator to return namedtuple from dictionary
print("The namedtuple instance from dict is  : ")
print(Student(**di))

Output :

The namedtuple instance using iterable is  : 
Student(name='Manjeet', age='19', DOB='411997')
The OrderedDict instance using namedtuple is  : 
OrderedDict([('name', 'Nandini'), ('age', '19'), ('DOB', '2541997')])
The namedtuple instance from dict is  : 
Student(name='Nikhil', age=19, DOB='1391997')

Additional Operation 

• _fields: This function is used to return all the keynames of the namespace declared.
• _replace(): _replace() is like str.replace() but targets named fields( does not modify the original values)

Python3

# Python code to demonstrate namedtuple() and
# _fields and _replace()

# importing "collections" for namedtuple()
import collections

# Declaring namedtuple()
Student = collections.namedtuple('Student', ['name', 'age', 'DOB'])

# Adding values
S = Student('Nandini', '19', '2541997')

# using _fields to display all the keynames of namedtuple()
print("All the fields of students are : ")
print(S._fields)

# ._replace returns a new namedtuple, it does not modify the original
print("returns a new namedtuple : ")
print(S._replace(name='Manjeet'))
# original namedtuple
print(S)

Output

All the fields of students are : 
('name', 'age', 'DOB')
returns a new namedtuple : 
Student(name='Manjeet', age='19', DOB='2541997')
Student(name='Nandini', age='19', DOB='2541997')

This article is contributed by Manjeet Singh. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or if you want to share more information about the topic discussed above. 

Using the collections module:

This approach creates a new namedtuple class using the namedtuple() function from the collections module. The first argument is the name of the new class, and the second argument is a list of field names.

Python3

from collections import namedtuple

Point = namedtuple('Point', ['x', 'y'])
p = Point(x=1, y=2)
print(p.x, p.y) # Output: 1 2

Output

1 2

Approach:
The code defines a named tuple called Point with two fields x and y. An instance of the Point class is then created with x=1 and y=2, and its x and y attributes are printed.

Time Complexity:
The time complexity of accessing an attribute of a named tuple is O(1), because it is a simple attribute lookup. Therefore, the time complexity of printing p.x and p.y is O(1) each.

Space Complexity:
The space complexity of the code is O(1) because it does not allocate any additional memory beyond what is required for the named tuple instance p and the Point class definition.

Overall, the code has a constant time and space complexity.