How to Get a List of Parameter Names for a Python Function?

Retrieving Parameter Names within Python Functions

In Python, introspecting a function's parameters can be useful for various purposes. One common question is how to programmatically obtain a list of the parameter names for a given function.

Built-in Python Methods

The inspect module provides comprehensive introspection capabilities for Python objects, including functions. However, the inspect.getargspec() and inspect.signature() methods, often used for retrieving parameter information, have been deprecated in Python 3.10 and later versions.

Alternative Approach Using Function Metadata

Fortunately, there's an alternative approach that leverages the underlying function metadata:

<code class="python">def list_parameter_names(func):
    """Returns a list of parameter names for a given function."""

    # Get the function's code object.
    code = func.__code__
    
    # The co_varnames attribute contains a tuple of parameter names.
    return code.co_varnames</code>

This code snippet defines a reusable function, list_parameter_names(), that takes a function as its argument and returns a list of its parameter names.

Usage Example

Here's an example demonstrating how to use the list_parameter_names() function:

<code class="python">def my_function(a, b, c):
    ...

parameter_names = list_parameter_names(my_function)
print(parameter_names)
# Output: ['a', 'b', 'c']</code>

Additional Considerations

Note that this method relies on the function's code object, which is an immutable object that cannot be modified. This means that any changes to the function's parameter list after its creation won't be reflected in the parameter names obtained through this method.

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