How to set an argument if it exists in the configuration file, and not include it if it does not exist.

In the case of else, there is a Type Error because you put NoneType where you need to put the dict.

definition(config:dict):
    If A in config:
        A=config ['A']
    else:
        A = None
    create_instance(
        OptionA=A
    )
create_instance(OptionA:dict):
....

What I want to do is to put a dict called config['A'] in option A of create_instance if there is a dict called A in the config, and if there is no dictation, I would like to do the same as putting nothing in the argument.

In the first place, I think it's wrong to put it in at a different point, but I'm worried about how to solve it.

As a provisional measure, I think there will be no problem, but if you do the same with other arguments when the create_instance argument becomes more than one, it will be full of ifs. I would appreciate it if you could let me know if there is any other good way.

 if A in config:
     A=config ['A']
    create_instance(
        OptionA=A
    )
else:
    A = None
    create_instance()