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# python-none-objects

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|    **A collection of "None" objects**    |
|:----------------------------------------:|
| **compatible with various Python types** |


The following code yields warning
for "Default argument value is mutable".

```python3
from typing import List, Dict

def foo(some: int, other: List = [], thing: Dict = {}):
    for o in other:
        bar(some, o, thing)
```

It is usually recommended to use None instead
(<https://stackoverflow.com/questions/41686829>
/why-does-pycharm-warn-about-mutable-default-arguments-
how-can-i-work-around-the):

```python3
from typing import List, Dict, Optional

def foo(
    some: int,
    other: Optional[List] = None,
    thing: Optional[Dict] = None,
):
    if other is None:
        other = []
    if thing is None:
        thing = {}
    for o in other:
        bar(some, o, thing)
```

But I prefer less boilerplate code like this:

```python3
from typing import Iterable, Mapping
from types import MappingProxyType

def foo(
    some: int,
    other: Iterable = (),
    thing: Mapping = MappingProxyType({}),
):
    for o in other:
        bar(some, o, thing)
```

This package introduces constants to make the code more readable:

```python3
from typing import Iterable, Mapping
from python_none_objects import NoneIterable, NoneMapping

def foo(
    some: int,
    other: Iterable = NoneIterable,
    thing: Mapping = NoneMapping,
):
    for o in other:
        bar(some, o, thing)
```

Be sure to look at the discussions on GitHub:
<https://github.com/LLyaudet/python-none-objects/discussions>.

There is a poll on the naming convention you would prefer:
<https://github.com/LLyaudet/python-none-objects/discussions/2>.

And there is a discussion on various ideas
to optimize the code with these constants:
<https://github.com/LLyaudet/python-none-objects/discussions/3>.

I think it would be better to have this kind of constants
in the standard library.
If you think after reading everything, that it is indeed a good idea,
add a star to this repository to let the rest
of the Python community
know that you would like to see such constant objects
in the language :).
<https://github.com/LLyaudet/python-none-objects/>
If the project gains popularity, I'll try to propose it officially.

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