namedtuple¶

A namedtuple is a tuple subclass with named fields. It combines the immutability of tuples with the readability of classes.

Creating Named Tuples¶

from collections import namedtuple

# Define the type
Scientist = namedtuple('Scientist', ['name', 'field', 'born', 'nobel'])

# Create instances
marie = Scientist('Marie Curie', 'physics', 1867, True)
einstein = Scientist(name='Albert Einstein', field='physics', born=1879, nobel=True)

Alternative Field Definitions¶

# Space-separated string
Point = namedtuple('Point', 'x y z')

# Comma-separated string
RGB = namedtuple('RGB', 'red, green, blue')

# List of strings
Person = namedtuple('Person', ['name', 'age', 'city'])

Accessing Fields¶

By Name (like class)¶

Scientist = namedtuple('Scientist', ['name', 'field', 'born', 'nobel'])
s = Scientist('Marie Curie', 'physics', 1867, True)

print(s.name)       # Marie Curie
print(s.field)      # physics
print(s.born)       # 1867
print(s.nobel)      # True

By Index (like tuple)¶

print(s[0])         # Marie Curie
print(s[1])         # physics
print(s[-1])        # True

Slicing¶

print(s[:2])        # ('Marie Curie', 'physics')
print(s[1:3])       # ('physics', 1867)

Immutability¶

Named tuples are immutable like regular tuples:

s = Scientist('Marie Curie', 'physics', 1867, True)

s.name = 'M Curie'  # AttributeError: can't set attribute
s[0] = 'M Curie'    # TypeError: 'Scientist' object does not support item assignment

Creating Modified Copies¶

Use _replace() to create a new instance with some fields changed:

s = Scientist('Marie Curie', 'physics', 1867, True)
s2 = s._replace(name='M. Curie', born=1867)
print(s2)           # Scientist(name='M. Curie', field='physics', born=1867, nobel=True)
print(s)            # Original unchanged

Comparison with Regular Class¶

Regular Class (Mutable)¶

class Scientist:
    def __init__(self, name, field, born, nobel):
        self.name = name
        self.field = field
        self.born = born
        self.nobel = nobel

s = Scientist('Marie Curie', 'physics', 1867, True)
s.name = 'M Curie'  # Works! (mutable)

namedtuple (Immutable)¶

from collections import namedtuple
Scientist = namedtuple('Scientist', ['name', 'field', 'born', 'nobel'])

s = Scientist('Marie Curie', 'physics', 1867, True)
s.name = 'M Curie'  # AttributeError (immutable)

Utility Methods¶

Named tuples provide special methods (prefixed with _):

`_fields`¶

print(Scientist._fields)    # ('name', 'field', 'born', 'nobel')

`_asdict()`¶

s = Scientist('Marie Curie', 'physics', 1867, True)
print(s._asdict())
# {'name': 'Marie Curie', 'field': 'physics', 'born': 1867, 'nobel': True}

`_make(iterable)`¶

data = ['Albert Einstein', 'physics', 1879, True]
einstein = Scientist._make(data)
print(einstein)     # Scientist(name='Albert Einstein', ...)

Default Values¶

Use defaults parameter (Python 3.7+):

Scientist = namedtuple('Scientist', ['name', 'field', 'born', 'nobel'], 
                       defaults=[None, False])

# 'born' defaults to None, 'nobel' defaults to False
s = Scientist('Marie Curie', 'physics')
print(s)            # Scientist(name='Marie Curie', field='physics', born=None, nobel=False)

Use Cases¶

Function Return Values¶

def get_user_info(user_id):
    UserInfo = namedtuple('UserInfo', ['name', 'email', 'active'])
    return UserInfo('Alice', 'alice@example.com', True)

info = get_user_info(123)
print(info.name)    # Alice (more readable than info[0])

Database Records¶

Row = namedtuple('Row', ['id', 'name', 'price'])
products = [
    Row(1, 'Apple', 1.50),
    Row(2, 'Banana', 0.75),
]
for p in products:
    print(f"{p.name}: ${p.price}")

Coordinates and Points¶

Point = namedtuple('Point', ['x', 'y'])
p1 = Point(3, 4)
p2 = Point(0, 0)
distance = ((p1.x - p2.x)**2 + (p1.y - p2.y)**2)**0.5

namedtuple vs typing.NamedTuple¶

For type hints, use typing.NamedTuple:

from typing import NamedTuple

class Scientist(NamedTuple):
    name: str
    field: str
    born: int
    nobel: bool = False     # Default value

s = Scientist('Marie Curie', 'physics', 1867)
print(s.nobel)              # False

Summary¶

Feature	tuple	namedtuple	class
Access by index	✅	✅	❌
Access by name	❌	✅	✅
Mutable	❌	❌	✅
Hashable	✅	✅	Depends
Memory	Low	Low	Higher

Use namedtuple when: - You need readable field names - Immutability is desired - Memory efficiency matters - Simple data container without methods