- 5.1 Function Definitions
- 5.2 Default Arguments
- 5.3 Variadic Arguments
- 5.4 Keyword Arguments
- 5.5 Variadic Keyword Arguments
- 5.6 Functions Accepting All Inputs
- 5.7 Positional-Only Arguments
- 5.8 Names, Documentation Strings, and Type Hints
- 5.9 Function Application and Parameter Passing
- 5.10 Return Values
- 5.11 Error Handling
- 5.12 Scoping Rules
- 5.13 Recursion
- 5.14 The lambda Expression
- 5.15 Higher-Order Functions
- 5.16 Argument Passing in Callback Functions
- 5.17 Returning Results from Callbacks
- 5.18 Decorators
- 5.19 Map, Filter, and Reduce
- 5.20 Function Introspection, Attributes, and Signatures
- 5.21 Environment Inspection
- 5.22 Dynamic Code Execution and Creation
- 5.23 Asynchronous Functions and await
- 5.24 Final Words: Thoughts on Functions and Composition
This chapter is from the book
This chapter is from the book
This chapter is from the book
5.5 Variadic Keyword Arguments
If the last argument of a function definition is prefixed with **, all the additional keyword arguments (those that don’t match any of the other parameter names) are placed in a dictionary and passed to the function. The order of items in this dictionary is guaranteed to match the order in which keyword arguments were provided.
Arbitrary keyword arguments might be useful for defining functions that accept a large number of potentially open-ended configuration options that would be too unwieldy to list as parameters. Here’s an example:
def make_table(data, **parms):
# Get configuration parameters from parms (a dict)
fgcolor = parms.pop('fgcolor', 'black')
bgcolor = parms.pop('bgcolor', 'white')
width = parms.pop('width', None)
...
# No more options
if parms:
raise TypeError(f'Unsupported configuration options {list(parms)}')
make_table(items, fgcolor='black', bgcolor='white', border=1,
borderstyle='grooved', cellpadding=10,
width=400)
The pop() method of a dictionary removes an item from a dictionary, returning a possible default value if it’s not defined. The parms.pop('fgcolor', 'black') expression used in this code mimics the behavior of a keyword argument specified with a default value.