How Can I Get the Parameter Names of a Python Function?

Obtaining Method Parameter Names using Python

When dealing with functions in Python, it can be convenient to obtain their argument names. Suppose we have a function named a_method defined as:

<code class="python">def a_method(arg1, arg2):
    pass</code>

To retrieve the argument names as a tuple of strings, we can utilize the inspect module.

<code class="python">import inspect

inspect.getfullargspec(a_method)</code>

This will return a tuple containing the argument names: ('arg1', 'arg2').

The inspect module provides additional insights into callable objects. For instance, if a function has default arguments or accepts variable-length arguments, the getfullargspec function will return information about those as well.

For example, the following function has a default argument and variable-length arguments:

<code class="python">def foo(a, b, c=4, *arglist, **keywords):
    pass</code>

inspect.getfullargspec will yield:

<code class="python">(['a', 'b', 'c'], 'arglist', 'keywords', (4,))</code>

This tuple indicates that c has a default value of 4, arglist is used for variable-length positional arguments, and keywords for variable-length keyword arguments.

In Python 3.3 and later, the inspect.signature function can be used to obtain the call signature of a callable object, including the argument names. For the example function foo:

<code class="python">inspect.signature(foo)</code>

This will return an Signature object providing detailed information about the function's signature.

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