limit function to only work with argument from a specific instance

Question

I have a function and I want the first positional argument of that only give the instances of a specific class , a code like this in other programming languages

from channels import Channel


def get_frame_link(Channel channel):
    print(channel)

if coder use that function in this way the python most raise an error

get_frame_link(123)
get_frame_link("hello")

the truth way most be only this

channel=Channel()
get_frame_link(channel)

note: this is not duplicated question because I don't asked for how to check a variable type

well you did basically asked how to check a variable's type as there is no other way to "block" Python from accepting any type as an argument... You have type-hints, but those are just helpers and the user can still do whatever he wants — Tomerikoo, Mar 08 '20 at 22:47

score 1 · Answer 1 · answered Mar 08 '20 at 22:30

1

Simply check that the type matches what you desire:

def get_frame_link(channel):
    if not isinstance(channel, Channel):
        raise TypeError("instance of type Channel expected")

    print(channel)

answered Mar 08 '20 at 22:30

donkopotamus

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limit function to only work with argument from a specific instance

1 Answers1