https://github.com/aloiziomacedo/stabledefaults

Allows for mutable defaults comfortably and intuitively.
https://github.com/aloiziomacedo/stabledefaults

decorators decorators-python functions python

Last synced: 2 days ago
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Allows for mutable defaults comfortably and intuitively.

• Host: GitHub
• URL: https://github.com/aloiziomacedo/stabledefaults
• Owner: AloizioMacedo
• License: mit
• Created: 2023-01-19T01:26:38.000Z (almost 2 years ago)
• Default Branch: master
• Last Pushed: 2023-01-20T02:15:43.000Z (almost 2 years ago)
• Last Synced: 2024-10-07T09:07:22.685Z (about 1 month ago)
• Topics: decorators, decorators-python, functions, python
• Language: Python
• Homepage: https://stabledefaults.readthedocs.io
• Size: 38.1 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Introduction

stabledefaults is a small package containing a decorator to allow for the expected behavior of lists, dicts and other mutable arguments in default arguments.

## Explanation

In Python, functions (as anything else) are objects, and the default arguments are stored as attributes that are initialized in definition.

Once this is known and the person understands that variables are references in Python, then it is relatively straightforward to understand the following behavior:

```python

def f(x=[]):

    x.append(2)

    return x

```

```python

>>> a = f()

>>> a

[2]

>>> f()

>>> a

[2, 2]

```

Nevertheless, this is unintuitive. Not only that, but dealing with this requires things such as

```python

def f(x = None):

    if x is None:

        x = []

    x.append(2)

    return x

```

which forces types such as ```list | None``` where just ```list``` should suffice, and also forces code inside the function itself.

This package solves this issue with a decorator. For instance, the example above would become

```python

@stabledefaults()

def f(x=[]):

    x.append(2)

    return x

```

```python

>>> a = f()

>>> a

[2]

>>> f()

>>> a

[2]

```