How to deprecate passing parameters positionally or by keyword

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Before anything else: why would you want to do this? Well, let’s say you have a function that takes five arguments two positional-only, three positional-or-keyword, and one keyword-only. But then, for some reason (let’s just say it’s because your boss told you so), you need to change the order of those positional-or-keyword parameters. Or maybe you want to make a parameter that was previously positional-or-keyword now be strictly keyword-only. Whatever the case may be, deprecating arguments is the way to go.

So how do we do it? Well, let’s take a look at an example:

# Define a function called myfunc with 5 parameters: a, b, c, d, and e
def myfunc(a, b, c=10, d=20, e):
    # The parameters a and b are positional parameters, while c, d, and e are keyword parameters
    # The default values for c and d are set to 10 and 20 respectively
    # The parameter e does not have a default value and must be provided by the user when calling the function
    # However, the order of the parameters can be changed when calling the function
    # To make a parameter strictly keyword-only, we can deprecate it
    # This means that the parameter can only be passed as a keyword argument and not as a positional argument
    # This is useful for making the code more readable and avoiding potential errors
    # To deprecate a parameter, we can add an asterisk before its name
    # In this case, the parameter e will be deprecated and can only be passed as a keyword argument
    # The function body will be defined later
    pass

Now, say you want to make the `b` parameter positional-only and the `d` parameter keyword-only. Here’s how you can do it:

# Import the necessary modules
from argparse import ArgumentParser  # Import the ArgumentParser class from the argparse module
import inspect  # Import the inspect module for accessing the remaining argument

# Define the function with one positional parameter
def myfunc(a):
    parser = ArgumentParser()  # Create an ArgumentParser object
    parser.add_argument('b', type=int)  # Add a positional-only argument 'b' of type int
    parser.add_argument('--c', type=int, default=10)  # Add a positional-or-keyword argument 'c' of type int with a default value of 10
    parser.add_argument('d', '--d', type=int, required=True)  # Add a keyword-only argument 'd' of type int that is required
    args = vars(parser.parse_args())  # Parse the arguments and store them in a dictionary
    
    e = args['e']  # Access the remaining argument (if any) using the dictionary
    
    # Function body here

# The function now has one positional-only parameter 'a', one positional-only parameter 'b', one positional-or-keyword parameter 'c' with a default value of 10, and one keyword-only parameter 'd' that is required. The remaining argument (if any) can be accessed using the dictionary 'args'.

Wait a minute what’s all this `argparse` stuff? Well, that’s because we want to make sure our new positional-only and keyword-only parameters are properly handled by Python. By using the `ArgumentParser`, we can ensure that any arguments passed in incorrectly will be caught and raised as an error.

But wait what if you don’t want to use `argparse`? What if you just want to deprecate passing arguments positionally or by keyword without all this extra hassle?

Introducing Argument Clinic: the ultimate tool for deprecating arguments like a boss. With Argument Clinic, you can generate code that makes it possible to generate code that deprecates passing arguments positionally or by keyword. It’s like a double-depreciation!

Here’s an example of how to use Argument Clinic:

# Import the necessary module
from argclinic import generate_function
import inspect

# Define the function to be deprecated
def myfunc(a, b=10, c=20):
    # function body here

# Define the new signature for our deprecated function
new_signature = {
    'positional-only': ['b'],  # make b positional-only
    'keyword-only': ['d']      # make d keyword-only
}

# Generate a new function with the updated signature
updated_func = generate_function(myfunc, new_signature)

# Get the source file of the original function and replace it with the updated function
# This ensures that the original function is replaced with the updated one
inspect.getsourcefile(myfunc).replace('def myfunc', 'def myfunc:\n' + str(updated_func), 1)

And there you have it a brand-new, deprecated version of your function! Of course, this is just an example and the exact implementation may vary depending on your specific use case. But with Argument Clinic, you can easily generate code that makes it possible to deprecate passing arguments positionally or by keyword in no time flat.

Whether you’re using `argparse` or Argument Clinic, the important thing is to make sure your code is properly handled and that any arguments passed incorrectly are caught and raised as an error.

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