Python Namedtuple Example

Use the namedtuple type from the collections module. A namedtuple is a tuple with field names.

Namedtuple. With tuples we store small groups of related fields together. A Point tuple, for example will have 2 coordinates: X and Y. The coordinates are part of a single unit.Tuple

To use namedtuple, we import the collections module. We specify the Type name. And we pass a string list of all the field names—these can then be directly used as fields.

An example. Here we create an Employee namedtuple with 3 fields. We pass a list to collections.namedtuple to specify field names id, title and salary.

Create: We create a namedtuple by using the Employee class name returned by collections.namedtuple.

Title: At the end of the program we access the "title" field with the syntax e.title: no index is required.

Python program that creates a namedtuple import collections # Specify the Employee namedtuple. Employee = collections.namedtuple("Employee", ["id", "title", "salary"]) # Create Employee instance. e = Employee(1, "engineer", 10000) # Display Employee. print(e) print("Title is", e.title) Output Employee(id=1, title='engineer', salary=10000) Title is engineer

Make method. Namedtuple offers extra methods—one of them is _make. With _make() we create a namedtuple from an iterable (like a list). The list elements are turned into tuple fields.

Tip: The make method fills namedtuple fields based on the order of the list's elements. So we must be careful with ordering.

List

Python program that uses _make method import collections # A namedtuple type. Style = collections.namedtuple("Style", ["color", "size", "width"]) # A list containing three values. values = ["red", 10, 15] # Make a namedtuple from the list. tuple = Style._make(values) print(tuple) Output Style(color='red', size=10, width=15)

Benchmark, namedtuple. This benchmark tests how long it takes to create a namedtuple versus a regular tuple. The results are not encouraging for namedtuple.

Version 1: This version of the code creates a namedtuple with 2 items in it. The code tests the first item in an if-statement.

Version 2: Here we create a tuple (not a namedtuple). We test the first item with an if-statement here as well.

Result: I found that namedtuple is several times slower in creation than a regular tuple.

Python program that benchmarks namedtuple, tuple import collections import time # The namedtuple instance. Animal = collections.namedtuple("Animal", ["size", "color"]) print(time.time()) # Version 1: create namedtuple. i = 0 while i < 10000000: a = Animal(100, "blue") if a[0] != 100: raise Exception() i += 1 print(time.time()) # Version 2: create tuple. i = 0 while i < 10000000: a = (100, "blue") if a[0] != 100: raise Exception() i += 1 print(time.time()) Output 1403288922.718007 1403288936.606831 namedtuple = 13.89 s 1403288939.667796 tuple = 3.06 s

Research. The Python documentation provides information about namedtuples. These are implemented in a similar way to regular tuples. So they do not use excess memory.

Quote: Named tuple instances do not have per-instance dictionaries, so they are lightweight and require no more memory than regular tuples.

Collections, namedtuple: python.org

A comparison. Even though namedtuple does not use excess memory, it involves more steps to initialize. And it requires a separate module (collections), making it harder to access.

In most programs, a tuple is a better choice than a named tuple. And for large groups of keys, a dictionary or set may be better. Namedtuple is limited in its use.

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Python Namedtuple Example

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