Python namedTuples

Python supports a type of container like dictionaries called “namedtuples()” present in module, “collection“. 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.

Operations on namedtuple() :Access Operations

1. 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.

2. Access by keyname : Access by keyname is also allowed as in dictionaries.

3. using getattr() :- This is yet another way to access the value by giving namedtuple and key value as its argument.

Example 1:

# 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

1. _make() :- This function is used to return a namedtuple() from the iterable passed as argument.

2. _asdict() :- This function returns the OrdereDict() as constructed from the mapped values of namedtuple().

3. using “**” (double star) operator :- This function is used to convert a dictionary into the namedtuple().

Example 2:

# 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 Operations

1. _fields :- This function is used to return all the keynames of the namespace declared.

2. _replace() :- This function is used to change the values mapped with the passed keyname.

Example 3:

# 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) 
  
# using _replace() to change the attribute values of namedtuple 
print ("The modified namedtuple is : ") 
print(S._replace(name = 'Manjeet')) 

Output:

All the fields of students are :

('name', 'age', 'DOB')

The modified namedtuple is :

Student(name='Manjeet', age='19', DOB='2541997')