When a function needs to accept an open-ended set of named options, **kwargs collects each name=value argument into a dictionary. The function can then inspect or transform those pairs instead of defining every parameter in advance. section 6.2
Building an XML-like tag
def myxml(tagname, content='', **kwargs): attrs = ''.join([f' {key}="{value}"' for key, value in kwargs.items()]) return f'<{tagname}{attrs}>{content}</{tagname}>' myxml('a', 'Read', href='page.html', class_='link') # '<a href="page.html" class_="link">Read</a>' Here, tagname is required, content defaults to an empty string, and kwargs holds the attribute pairs. Iterating over kwargs.items() converts the dictionary into formatted attribute text. section 6.2
The same pattern can construct a dispatch table dynamically: keyword names become menu options, and their values become the functions invoked for those options. A dictionary argument would also work, but **kwargs provides a direct call syntax. section 8.7
Use **kwargs when:
- The accepted keyword names are intentionally open-ended, such as XML-like attributes. section 6.2
- Keyword names should be turned into a configurable mapping, such as menu options connected to zero-argument functions. section 8.7
- A fixed set of supported filters is preferable when the method deliberately accepts only names such as color and legs. section 9.40
def myxml(tagname, content='', **kwargs):
attrs = ''.join([f' {key}="{value}"'
for key, value in kwargs.items()])
return f'<{tagname}{attrs}>{content}</{tagname}>'
Inspect the complete progression from required tag name and optional content to arbitrary keyword attributes. section 6.2
