This content originally appeared on DEV Community and was authored by Kathan Vakharia
Introduction
As it has tuple in it's name, one thing is clear that it will add some superpower?♀️ to the tuples.
namedtuple is a special type of tuple that has named indices. Ofcourse, they also have normal integer indices as they are tuples anway.
Importing namedtuple
from collections import namedtuple
namedtuple creation
# Step 1: Define namedtuple
# 'typename'=> used when printing an obj & low-lvl stuff
# 'fieldnames'=> list of names of indices
Student = namedtuple(typename='Student',
field_names=['fname', 'lname', 'age']
)
# Step 2: Create a namedtuple
# explicitly assigning named indices
s1 = Student(fname="Shan", lname="Patel", age=19)
# named indices are inferred
s2 = Student("Kathan", "Vakharia", 19)
print(s1, s2, sep='\n')
"""OUTPUT
Student(fname='Shan', lname='Patel', age=19)
Student(fname='Kathan', lname='Vakharia', age=19)
"""
? It is important to note that the identifier you use for defining the
namedtuple(Student here) is the one you have to use while instantiating anamedtuple. It has nothing to do with thetypenameargument-It's just a name for your custom tuple sub-class.
Quoting the python documentation,
collections.namedtuple(typename, field_names,...)
- Returns a new tuple subclass named typename.
We can cross-verify if we want using issubclass function.
>>> issubclass(Student, tuple) True
# CORRECT WAY
s0 = Student("heet", "vakharia")
print(s0)
"""OUTPUT
blah(fname='heet', lname='vakharia')
""""
# INCORRECT way
Student = namedtuple(typename="blah",
field_names=["fname", "lname"]
)
s1 = blah("kathan", "vakharia")
"""OUTPUT
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'blah' is not defined
"""
Indexing namedtuples
Indexing namedtuple object is very straight-forward. Here's how you do it,
# way1 : using integer indices
# Same like 'plain-tuples'
print("First element of s1: {}"
.format(s1[0]))
# way 2: using named indices 'NEW'
print("Element of s2 having named index lname: {}"
.format(s2.lname))
"""OUTPUT
First element of s1: Shan
Element of s2 having named index lname: Vakharia
"""
As it is a sub-class of tuple, it inherits all the methods and attributs of tuple.
However, there are some interesting methods pertaining to namedtuple. Let's see what are those,
classmethod somenamedtuple._make(iterable)
fields = ["John", "Doe", 34]
print(Student._make(fields))
"""OUTPUT
Student(fname='John', lname='Doe', age=34)
"""
somenamedtuple._asdict()
Returns a new dict which maps field names to their corresponding values,
from collections import namedtuple
Student = namedtuple(typename='Student',
field_names=['fname', 'lname', 'age'],
)
shan = Student(fname="Shan", lname="Patel", age=19)
kathan = Student("Kathan", "Vakharia", 19)
# namedtuple._asdict()
print(shan._asdict())
print(kathan._asdict())
"""OUTPUT
{'fname': 'Shan', 'lname': 'Patel', 'age': 19}
{'fname': 'Kathan', 'lname': 'Vakharia', 'age': 19}
"""
somenamedtuple._replace(**kwargs)
Returns a new instance of the named tuple replacing specified fields with new values.
kathan = Student("Kathan", "Vakharia", 19)
# a new tuple will be created with changed fname
kathan_v2 = kathan._replace(fname="Karsh")
print(kathan_v2)
# Old kathan is still unchanged
print(kathan)
"""OUTPUT
Student(fname='Karsh', lname='Vakharia', age=19)
Student(fname='Kathan', lname='Vakharia', age=19)
"""
And that wraps our discussion on namedtuple. I have intentionally left some minor functionalities because they are too trivial :) However, feel free to check out the documentation for that remaining 5% stuff.
This content originally appeared on DEV Community and was authored by Kathan Vakharia
Kathan Vakharia | Sciencx (2021-06-18T18:26:54+00:00) Python’s Collections Module: namedtuple. Retrieved from https://www.scien.cx/2021/06/18/pythons-collections-module-namedtuple/
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