Discussion on: API Design: Optional Parameters

[rhymes]

Really good article, thank you Sam!

[Sam Rose]

Thank you so much! I'm glad you enjoyed it. If you don't mind, could you spare a few minutes to tell me things you like and didn't like? I'm looking to level up my writing. :)

[rhymes]

ahha nothing I didn't like, the builder in Java is very verbose :D

BTW a little trick by more recent Python versions. You explained the problem with optional parameters, because you can do things like this:

>>> def get(url, follow_redirects=False, headers=None):
...     pass
...
>>> get("https://example.com")
>>> get("foobar", 3)

And for a reader it's not easy to know if 3 is referred to either parameter, or at least is not explicit at all which makes life complicated with many arguments to specify.

Since recently you can do this:

>>> def get(url, *, follow_redirects=False, headers=None):
...     pass
...
>>> get("foobar")
>>> get("foobar", True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: get() takes 1 positional argument but 2 were given
>>> get("foobar", follow_redirects=True)

The compiler now forces you to specify the name of each optional argument

[Sam Rose]

Oh that's super nice, I had no idea that was possible!

[rhymes]

Yeah, it can also become a catch all for all unnamed optional parameters.

>>> def get(url, *args, follow_redirects=False, headers=None):
...     print(f"u: {url}, a: {args}, f: {follow_redirects}, h: {headers}")
...
>>> get("https://dev.to")
u: https://dev.to, a: (), f: False, h: None
>>> get("https://dev.to", 1, 2, 3)
u: https://dev.to, a: (1, 2, 3), f: False, h: None
>>> get("https://dev.to", 1, 2, 3, follow_redirects=True, headers={"user-agent": "acme"})
u: https://dev.to, a: (1, 2, 3), f: True, h: {'user-agent': 'acme'}
>>> get("https://dev.to", follow_redirects=True, headers={"user-agent": "acme"})
u: https://dev.to, a: (), f: True, h: {'user-agent': 'acme'}