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')

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