18. Keyword-only arguments

Few times being explicit is better which increases the readability of code. If a function signature has Keyword-only arguments, then while calling the function, we need to pass our objects by their keyword names. PEP-3102 defines the Keyword-only arguments.

Well, how to define the keyword only arguments 🤔? In the previous lesson about Positional Arguments we have seen that Positional-only Arguments whose function signature is created by using /. Similarly for Keyword-only Argument, we use * in the signature.

def keyword_only_argument_signature(*, arg1, arg2):
    ...

Example:

def greet(*, greet_word, name):
    print(f"{greet_word} {name}!")

Now if we want to try calling our new function greet as greet("Hello", "Pythonist♥️"), we should be seeing a TypeError.

greet("Hello", "Pythonist ♥️")

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[2], line 1
----> 1 greet("Hello", "Pythonist ♥️")

TypeError: greet() takes 0 positional arguments but 2 were given

The only way we can call our greet function is by passing our both greet_word and name values with keyword names.

greet(greet_word="Hello", name="Pythonist ♥️")

Hello Pythonist ♥️!