Set an attribute for all instances of a class under conditions

First of all, excuse my ignorance if this is a fairly easy question. What I would like to achieve is to create an attribute for every instance of the class (i.e. filepath), change it for an instance (i.e. in the first case, where I change the value of filepath for the a instance, but if I create a new instance, e.g. b I would like to keep the original filepath value.

filepath = '/path/to/original/file'

class A(object):


    @classmethod
    def _set_path(cls, filepath):
        cls.filepath = filepath
        return cls.filepath

    def __init__(self, name):
        self.name = name

A._set_path(filepath) # Set filepath for all instances: /path/to/original/file

a = A("Alice")
print(a.filepath)
a._set_path("/path/to/another/file") # Set filepath for instance a, but the way I've written the code the filepath value will be the new one
                                    # for every new instance.
print(a.filepath)

b = A("Bob")
print(b.filepath) # I would like to keep /path/to/original/file

Is there a way to improve this code and/or have a smart design pattern for this case?