Python - Class object as function argument: Object only - Class not in argument

Question

I am trying to write a function taking a string as an argument and using this argument as a class object.

Note that my explanantion might be strangely formulated sice I could not find an answer online. The MWE below should clarify what I mean, the problematic line is indicated.

Edit: in the MWE, "print" is an example. I need to be able to call the object to update it, print it or, in the case of a list, append to it. I need access to the object itself, not the value of the object.

MWE

# Create a class
class myClass():
    def __init__(self):
        self.one = "Test"
        self.two = "Plop"

# Define function
def myFunction (parameter):
    print(myObject.parameter)##### This line is currently not possible.

# Use class
myObject = myClass()

# Use function
myFunction("one")

I am not trying to append a new object to the class, only to call an existing object.

Is this even possible?

Andrew Menshicov · Accepted Answer · 2022-10-25 14:53:48Z

2

Looks like you need the built-in function called getattr

my_object = myClass()

def my_function(parameter):
    print(getattr(my_object, parameter, None))

also this is not the best practice to call objects from outer scope like that. i'd suggest to use dict magic methods:

class MyClass:
    def __init__(self):
        self.one = "Test"
        self.two = "Plop"

    def __getitem__(self, parameter):
        return getattr(self, parameter, None)

    def __setitem__(self, parameter, value):
        return setattr(self, parameter, value)

my_obj = MyClass()
parameter = "x"
print(my_obj[parameter])
my_obj[parameter] = "test"
print(my_obj.x)

edited Oct 25, 2022 at 14:53

answered Oct 25, 2022 at 8:52

Andrew Menshicov

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7 Comments

AlMa Over a year ago

No, this is not what I want to do. It works for the "print" example, but I want to be able to manipulate the object itself, not just access its current value.

Andrew Menshicov Over a year ago

@AlMa you can do this too, via accessing self.__dict__. like this: my_object.__dict__["one"] = "Test1"

Andrew Menshicov Over a year ago

@AlMa but this is not the best thing to do. better ways is inheriting from dict so that you can do whatever you want like my_object[parameter]=1

AlMa Over a year ago

Thank you, accessing self.__dict__ works perfecly. What do you mean by "inheriting from dict"? If I try my_object[parameter]=1 I get the error message "TypeError: 'myClass' object is not subscriptable"

Andrew Menshicov Over a year ago

@AlMa i checked and looks like inheriting from dict doesn't work as i expected. if you want to be able to use my_object[parameter]=1, you need to override the magic methods __setitem__ and __getitem__

|

SKY · Accepted Answer · 2022-10-25 09:06:53Z

0

You need to use getarttr():

# Create a class
class myClass():
    def __init__(self):
        self.one = "Test"
        self.two = "Plop"




# Use class
myObject = myClass()

# Define function
def myFunction(parameter):
    print(getattr(myObject, parameter))##### This line is currently possible.


# Use function
myFunction("one")

answered Oct 25, 2022 at 9:06

SKY

1772 silver badges8 bronze badges

3 Comments

AlMa Over a year ago

No, this is not what I want to do. It works for the "print" example, but I want to be able to manipulate the object itself, not just access its current value.

SKY Over a year ago

Can you give an example what you want to do? You post lacks clarity.

AlMa Over a year ago

See the edit of my post.

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