A function argument is a value supplied at a call site for a corresponding parameter. Python supports required arguments, optional arguments with defaults, positional expansion with *, and keyword expansion with **. section 2.7 section 7.3
Choose the argument form according to the function’s input contract:
- Use named parameters for a known set of values; use a default when an argument is optional. section 7.3
- Use *args when the number of positional values is unknown and the function will process the resulting tuple iteratively. section 2.7
- Prefix an iterable with * at the call site to turn its elements into separate positional arguments. section 2.7
- Use **kwargs to collect arbitrary name=value arguments in a dictionary for keyword-based processing. section 7.3
Unpacking a sequence
Calling mysum([1, 2, 3]) passes one argument—the list—whereas mysum(*[1, 2, 3]) passes three numeric arguments. The first form can therefore produce a TypeError when the function adds its arguments. section 2.7
def myxml(tagname, content='', **kwargs):
attrs = ''.join([f' {key}="{value}"'
for key, value in kwargs.items()])
return f'<{tagname}{attrs}>{content}</{tagname}>'
A function combines a required argument, an optional defaulted argument, and keyword arguments while converting the collected dictionary into XML attributes. section 7.3
