This is because typing.NamedTuple is not really a proper type. It is a class. But its singular purpose is to take advantage of meta-class magic to give you a convenient nice way to define named-tuple types. And named-tuples derive from tuple directly. Note, unlike most other classes, from typing import NamedTuple class Foo(NamedTuple): pass print(isinstance(Foo(), … Read more
To create the subclass, you may just pass the keys of a dict directly: MyTuple = namedtuple(‘MyTuple’, d) Now to create tuple instances from this dict, or any other dict with matching keys: my_tuple = MyTuple(**d) Beware: namedtuples compare on values only (ordered). They are designed to be a drop-in replacement for regular tuples, with … Read more
The prefered Syntax for a typed named tuple since 3.6 is from typing import NamedTuple class Point(NamedTuple): x: int y: int = 1 # Set default value Point(3) # -> Point(x=3, y=1) Edit Starting Python 3.7, consider using dataclasses (your IDE may not yet support them for static type checking): from dataclasses import dataclass @dataclass … Read more
Create the named tuple outside of the function: from collections import namedtuple import pickle P = namedtuple(“P”, “one two three four”) def pickle_test(): my_list = [] abe = P(“abraham”, “lincoln”, “vampire”, “hunter”) my_list.append(abe) with open(‘abe.pickle’, ‘wb’) as f: pickle.dump(abe, f) pickle_test() Now pickle can find it; it is a module global now. When unpickling, all … Read more
This is a typical late binding issue (see common gotchas): when the functions (being lambda/anonymous has nothing to do with it) are called, they access the current value of item, which is the last one from the loop. Try lambda x=item: x.data in your loop instead. This works since default arguments are bound to a … Read more
from operator import attrgetter from collections import namedtuple Person = namedtuple(‘Person’, ‘name age score’) seq = [Person(name=”nick”, age=23, score=100), Person(name=”bob”, age=25, score=200)] Sort list by name sorted(seq, key=attrgetter(‘name’)) Sort list by age sorted(seq, key=attrgetter(‘age’))
TL;DR: there’s a method _asdict provided for this. Here is a demonstration of the usage: >>> fields = [‘name’, ‘population’, ‘coordinates’, ‘capital’, ‘state_bird’] >>> Town = collections.namedtuple(‘Town’, fields) >>> funkytown = Town(‘funky’, 300, ‘somewhere’, ‘lipps’, ‘chicken’) >>> funkytown._asdict() OrderedDict([(‘name’, ‘funky’), (‘population’, 300), (‘coordinates’, ‘somewhere’), (‘capital’, ‘lipps’), (‘state_bird’, ‘chicken’)]) This is a documented method of namedtuples, … Read more
The way named tuples are constructed make inheritance from typing.NamedTuple classes as yet not possible. You’d have to write your own metaclass to extend the typing.NamedTupleMeta class to make subclassing work, and even then the class generated by collections.namedtuple() is just not built to extend. Instead, you want to use the new dataclasses module to … Read more
In a function call *t means “treat the elements of this iterable as positional arguments to this function call.” def foo(x, y): print(x, y) >>> t = (1, 2) >>> foo(*t) 1 2 Since v3.5, you can also do this in a list/tuple/set literals: >>> [1, *(2, 3), 4] [1, 2, 3, 4] **d means … Read more
There is a mutable alternative to collections.namedtuple – recordclass. It can be installed from PyPI: pip3 install recordclass It has the same API and memory footprint as namedtuple and it supports assignments (It should be faster as well). For example: from recordclass import recordclass Point = recordclass(‘Point’, ‘x y’) >>> p = Point(1, 2) >>> … Read more