Mutable NamedTuple in python

Question

I’m looking for a good struct pattern in python. The NamedTuple class constructor is almost what I want. Consider the following:

class MyStruct(NamedTuple):
  prop1: str
  prop2: str
  prop3: Optional[str] = "prop3" # should allow default values
  prop4: Optional[str] = "prop4"
  ...

# allow this
struct = MyStruct(prop1="prop1", prop2="prop2")

# allow this (order agnostic)
struct = MyStruct(prop2="prop2", prop1="prop1")

# allow this (supply value to optional properties)
struct = MyStruct(prop1="prop1", prop2="prop2", prop3="hello")

# allow this (access via . syntax)
print(struct.prop3)

# allow this (mutate properties)
struct.prop2 = "hello!"

# don't allow this (missing required properties, prop1 and prop2)
struct = MyStruct()

NamedTuple does everything except the mutability piece. I’m looking for something similar to a Namespace with type hints. I looked at TypedDict as well, but don’t like that you can’t access properties with struct.prop1, but instead must use struct["prop1"]. I also need to be able to supply default values when the struct is instantiated.

I thought about just a regular class as well, but my object may have many properties (20-30), and the order in which properties are supplied to the constructor should not matter.

I also want type hinting in my editor.

What’s the best way to achieve this?

Asked By: CaptainStiggz

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Source

Answer 1

You can use @dataclass:

from dataclasses import dataclass
from typing import Optional


@dataclass
class MyStruct:
    prop1: str
    prop2: str
    prop3: Optional[str] = "prop3"
    prop4: Optional[str] = "prop4"

Answered By: Unmitigated

Answer 2

If dataclass doesn’t satisfy your requirements, try recordclass, literally a mutable named tuple.

Answered By: JustLearning

Mutable NamedTuple in python

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