cmgurba / python-parameter-talk Goto Github PK

This is a short set of examples to show how Python parameters work. It has a specific point of showing how kwargs work.

Showing the differences between:

• keyword argument vs keyword parameter
• argument defaults and behavior

Just because have names does not mean you must specify them. These can be viewed as positional parameters. Note, all parameters are position, however, some may have default values.

If a default value is given to a parameter is not a keyword argument. It is just a parameter with a default value. This means you do not need to specify a value for the parameter.

The order of keyword arguments is irrelevant. As long as positional arguments are satisfied first the ordering of the named parameters with default values does not matter.

So when using keyword arguments the position of arguments does not matter.

A bit on how **kwargs work. That **kwargs is a special "gobble" up the rest of the keyword arguments.

A bit on how *args work. That *args is a special "gobble" up the rest of the positional arguments.

Default values are not always the same. Python keeps default values assigned to parameters the same, respecting the rules of mutable data types.

Take a look at fib.py, fib_cached.py, and fib_cached_broken.py.

It's an example of why this behavior can be useful and why it works how it does work. Specifically the known_values being modified vs reassigned effects how the default parameter works. If the value is reassigned it does not effect the default parameter because the parameter is not modified. When known_values.append is used the default parameter is changed. This because the actual value is modified.