Python get function signature

Python — Get Function Signature

Understanding function signatures in Python is essential for unraveling the inner workings of functions. The inspect module offers a range of methods to retrieve signatures, allowing you to analyze parameters, access data types, and determine default values. By exploring these techniques, you can gain valuable insights that enhance code readability, maintainability, and documentation. So, dive into the world of function signatures and unlock a deeper understanding of your Python code.

Using inspect Method

The inspect method provides a powerful way to retrieve the function signatures. This method enables us to access detailed information about a function’s parameters, data types, default values, and more. This helps the developers know better about the function, requirements, and properties.

Example

We first imported the inspect module using the import statement in the following code. Next, we created a void function named my_function which takes a couple of arguments and their hints. We created an object with the signature method of inspect module and passed the my_functionn as the argument. Next, we used the parameters method to access the details of the parameters. We iterated over the return value and printed it.

import inspect def my_function(arg1: int, arg2: str, *args: int, **kwargs: float) -> bool: pass signature = inspect.signature(my_function) params = signature.parameters for name, param in params.items(): print(f"Parameter: ") print(f"Type: ") print(f"Default Value: ") print(f"Kind: ") print("---")

Output

Parameter: arg1 Type: Default Value: Kind: POSITIONAL_OR_KEYWORD --- Parameter: arg2 Type: Default Value: Kind: POSITIONAL_OR_KEYWORD --- Parameter: args Type: Default Value: Kind: VAR_POSITIONAL --- Parameter: kwargs Type: Default Value: Kind: VAR_KEYWORD --- 

Using the inspect module’s getfullargspec function

The getfullargspec function of the inspect module is another method that we can use to retrieve comprehensive information about the function’s arguments. It provides a detailed analysis of both the positional and keyword arguments. It also supports the variable arguments and keyword arguments.

Example

In the following code, we imported the inspect library and defined a user-defined function named my_function. Next, we created an object named argspec using the getfullargspec method. We passed our function as the argument. Next, we used the zip method to combine the argument details and the annotation values and for the loop to iterate and print the results.

import inspect def my_function(arg1: int, arg2: str, *args: int, **kwargs: float) -> bool: pass argspec = inspect.getfullargspec(my_function) for name, annotation in zip(argspec.args, argspec.annotations.values()): print(f"Parameter: ") print(f"Type: ") print("---")

Output

Parameter: arg1 Type: --- Parameter: arg2 Type: ---

Conclusion

Understanding function signatures in Python is essential for unraveling the inner workings of functions. The inspect module offers a range of methods to retrieve signatures, allowing you to analyze parameters, access data types, and determine default values. By exploring these techniques, you can gain valuable insights that enhance code readability, maintainability, and documentation. So, dive into the world of function signatures and unlock a deeper understanding of your Python code.

Источник

Get Function Signature

1. Use signature() to Get Function Call Details in Python
2. Use Decorators to Get Function Call Details in Python

This tutorial will discuss a couple of methods for getting function call details quickly using Python. This is particularly useful when analyzing a large codebase, and figuring out what a function is doing at a glance becomes difficult.

Instead of going back and forth through the code, we have smarter solutions for this exact problem using signature() functions and decorators.

Use signature() to Get Function Call Details in Python

The easiest way to get this information is by using inspect.signature() function. The document for Python 3.5+ recommends using this function.

inspect.signature() accepts a variety of callables. This includes functions, classes and functools.partial() objects.

The function returns the callable’s annotation. If no signature can be provided, the function raises a ValueError ; if the object type is not supported, it raises a TypeError .

import inspect  def foo(x, y, a="anything"):  pass  print(inspect.signature(foo)) 

It should print the following on your terminal.

Use Decorators to Get Function Call Details in Python

Functions in Python have a few attributes that we can make use of. Among these attributes is __code__ .

The __code__ attribute further has attributes we can use. Below, you can find each of them listed, explaining what they do.

co_varnames returns a tuple of the names of the arguments passed to the function and the local variables used inside the function.

co_argcount returns the number of arguments. However, this count excludes the keyword-only arguments ( kwargs ), *args , and **args .

def get_func_dets(func):  # the point of using argcount is to ensure we only get  argument_names = func.__code__.co_varnames[:func.__code__.co_argcount]  func_name = func.__name__   # getting variable length arguments and keyword arguments  def inner_fun(*args, **kwargs):  print(func_name, "(", end = "")   print(", ".join('%s = %r' % ent  for ent in zip(argument_names, args[:len(argument_names)])), end=", ")   print("args = ", list(args[len(argument_names):]), end=",")  print("kwargs =", kwargs, end="")  print(")")   return inner_func 

Husnain is a professional Software Engineer and a researcher who loves to learn, build, write, and teach. Having worked various jobs in the IT industry, he especially enjoys finding ways to express complex ideas in simple ways through his content. In his free time, Husnain unwinds by thinking about tech fiction to solve problems around him.

Related Article — Python Function

Источник