Python样式，命名常量参数

Question

I'm thinking of spelling those Python function arguments that are not modified in the function body as ALL_UPPERCASE, signaling to users of such an API that the passed value won't be modified (if everything goes as advertised, at any rate). I'm unaware of Python conventions or language mechanisms that this would collide with; are there any? Would such a naming convention be advisable, or just unnecessarily odd?

Eg:

def foo(bar, BAZ):
    return bar.some_method(BAZ.some_property)

Answer 1

UPPERCASE is for global constants, not function arguments. See the Python Style Guide here.

In Python function signatures, you'd expect all arguments to be unmodified. If an argument expects a mutable object and it'll be changed in-place, then that is the exception and should be documented as such:

def foo(bar, baz):
    """Frobs the bar in baz

    Alters the baz list in-place, and returns None.

    """

Using UPPERCASE for function arguments that are not being modified would thus be a) confusing (as it conflicts with the style guide) and b) redundant, as most code won't alter mutable objects in place unless documented as doing so explicitly.