How to Preserve Function Signatures with Python Decorators?

Preserving Function Signatures with Decorators

Decorators are a powerful tool in Python, but they can also introduce problems with decorated function signatures. To preserve the original function's signature, consider the following approaches:

Approach 1: decorator module

Install the decorator module (pip install decorator) and adapt your decorator to use its @decorator.decorator syntax:

<code class="python">import decorator

@decorator.decorator
def args_as_ints(f, *args, **kwargs):
    args = [int(x) for x in args]
    kwargs = dict((k, int(v)) for k, v in kwargs.items())
    return f(*args, **kwargs)</code>

Approach 2: functools.wraps() (Python 3.4 )

Python 3.4 introduced functools.wraps(), which preserves function signatures:

<code class="python">import functools

def args_as_ints(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        args = [int(x) for x in args]
        kwargs = dict((k, int(v)) for k, v in kwargs.items())
        return func(*args, **kwargs)
    return wrapper</code>

Both approaches effectively preserve the function signature after decoration. Additionally, functools.wraps() can be used for compatibility with older Python versions.

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