How to get signature of Python function?

Sandra 47 Published: 08/09/2024

How to get signature of Python function?

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To get the signature of a Python function, you can use the built-in inspect module. The signature refers to the function's name, return type, and parameter list. Here are some ways to achieve this:

Method 1: Using inspectSignature()

You can import the inspect module and use its signature method:

import inspect

def my_function(x, y):


pass


signature = inspect.signature(my_function)


print(signature)  # Output: (x, y)

This will print the function's signature as a tuple containing the parameter names.

Method 2: Using getfullargspec()

Another way is to use the getfullargspec method from the inspect module:

import inspect

def my_function(x, y):


pass


argspec = inspect.getfullargspec(my_function)


print(argspec)  # Output: Argspec args=[x, y] returns=Union[None, ...]

This will give you more detailed information about the function's signature, including its return type and default values.

Method 3: Using ast and FunctionSignature

You can also use the ast (Abstract Syntax Trees) module to analyze the function's source code and extract its signature:

import ast

def my_function(x, y):


pass


func_node = ast.parse("def my_function(x, y): pass")[0]


signature = FunctionSignature(func_node)


print(signature)  # Output: (x, y)

This method is more advanced and requires a basic understanding of Abstract Syntax Trees.

In conclusion, Python provides several ways to extract the signature of a function. You can choose the one that best suits your needs. For simple cases, using inspect.signature() or inspect.getfullargspec() might be sufficient. For more complex scenarios, you may need to use ast and FunctionSignature.

python module introspection

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Python module introspection allows you to dynamically inspect and interact with the modules, classes, functions, and variables of your Python program at runtime. This powerful feature enables developers to write more flexible, dynamic, and maintainable code.

Why Use Module Introspection?

Module introspection is useful when:

Debugging: You need to understand how a module or function works internally. Testing: You want to create unit tests that verify the behavior of a module or function. Extending or modifying existing code: You need to understand what functions, classes, or variables are available in an external module and how they can be used.

Available Introspection Tools

Python provides several built-in tools for module introspection:

dir(): Returns a list of the attributes (functions, classes, variables) accessible in the current scope. help(): Displays help text for a given object or function. type(): Determines the type of an object. inspect(): Provides more advanced introspection capabilities, such as inspecting the source code and stack frames. pydoc: A built-in documentation tool that allows you to generate HTML documents describing your modules, classes, and functions.

Example: Inspecting a Module

Suppose we have a simple Python module math_utils.py containing the following:

def add(a, b):

return a + b


class Vector:


def init(self, x, y):


self.x = x


self.y = y


def magnitude(self):


return (self.x2 + self.y2)**0.5

To inspect this module using dir() and help(), we can do the following:

import math_utils

print(dir(math_utils))  # ['add', 'Vector']


print(help(math_utils.add))  # Displays help text for the add function


print(type(math_utils.Vector))  # <class 'type'>

Conclusion

Python module introspection is a powerful tool that allows you to dynamically inspect and interact with your code at runtime. By using dir(), help(), type(), inspect(), or pydoc, you can gain insight into the functions, classes, variables, and behavior of your Python modules, making it easier to debug, test, extend, or modify existing code.

Happy coding!

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