partial-readonly 0.0.3

make some of the dataclass fields read-only

partial readonly

partial_readonly provide a decorator for conveniently making some fields read-only in dataclass. No dependencies other than the Python Standard Library.

Usage

Quick Start

With partail_readonly, we can easily make some of the fields in dataclass read-only by creating property related to them. (Notice: We still can't make the origin field read-only, cause it still need to be set while calling __init__)

For example, the following code

from dataclasses import dataclass

@dataclass
class Data:
    id: int = 0
    name: str = ''

    @property
    def full_name(self): return self.name

can be written like this by using partial_readonly

from dataclasses import dataclass

@dataclass
class Data:
    id: int = 0
    _name: 'str alias=full_name' = ''

Details

1. Mark a field read-only by adding an underline prefix
   • _id: int means id is read-only
2. By default, the relative property named like field without underline prefix
   • _id: int will generate a property named id
3. Use string annotation and add alias=alias_you_want at the end, and you'll have a property named alias_you_want
   • _id: 'int alias=security_id will generate a property named security_id

Installation

To install partial_readonly, simply use pip:

pip install partial_readonly

Or use easy_install:

easy_install partial_readonly

Deep down

1. Making property read-only by set a getter[ and ban a setter]
2. Using AST to build a getter for new property
3. The idea about abusing annotation comes from zmitchell/annotation-abuse

Why partial_readonly

Lastest python offer us dataclass for creating some class in convenient way.

But it's not convenient when we want not all the fields be readonly.

Requirements

• Python >= 3.7

Postscript

I built this for practicing AST and publish.

I think it work fine.

There are some more easily implementation.

If you sharing some idea about this feature I'll be greatful!

License

MIT License

Copyright (c) 2018 book987

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