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) |
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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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 |
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.
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