ReactCHALLENGES

9. Double-star kwargs

**kwargs lets a function accept any number of keyword arguments. The ** before the parameter name collects them into a dictionary:

Inside the function, data is a dictionary: show(name="Ada", age=36) makes it {"name": "Ada", "age": 36}.

** does two jobs depending on where it appears:

  • In the definition def show(**data), it packs all keyword arguments into the dictionary data.
  • In a call, show(**{"name": "Ada", "age": 36}) unpacks that dictionary into keyword arguments. It is exactly the same as show(name="Ada", age=36).

You cannot call show({"name": "Ada", "age": 36}): that passes one positional argument, and def show(**data) only accepts keyword arguments.

*args from the previous lesson is the positional counterpart: def f(*numbers) packs positional arguments into a tuple, and f(*[1, 2, 3]) unpacks a list into positional arguments.

  • Only keyword arguments are collected; positional arguments are not.
  • The name kwargs is a convention; the ** is what matters.
  • Regular parameters, *args and **kwargs can be combined in that order.

Coming from JavaScript? **kwargs collects extra named options into a dict, not an object. At the call site, f(**data) spreads that dict into named arguments, similar to spreading an object into props.

#01

Collect keyword arguments

Define show(**data) that loops over data.items() and prints each pair as key: value using an f-string. Call show(name="Ada", age=36).

Print exactly:

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#02

Count the keyword arguments

Define count_kwargs(**info). The ** collects the keyword arguments into the dictionary info, so len(info) returns how many keyword arguments were passed. The function should return that number.

Then print count_kwargs(a=1, b=2, c=3).

Print exactly:

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#03

Read one keyword argument

Define welcome(**info) that prints Welcome to <city> using info["city"]. Call welcome(city="Paris").

Print exactly:

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#04

Add the keyword values

Define total_points(**scores) that adds every value in scores with a for loop and returns the total. Print total_points(math=90, art=80).

Print exactly:

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