python initialize class and base class using class method

Question

I am trying to initialize a derived class from text file input. A simple example of what I am trying to do:

file.txt:

1
2

main.py:

class Base:
 def __init__(self, val1):
 self.val1 = val1
 def input_from_text(cls, init_deque):
 #return cls(init_deque.popleft())
class Derived(Base):
 def __init__(self, val1, val2):
 Base.__init__(self, val1)
 self.val2 = val2
 def input_from_text(cls, init_deque):
 #initialize base and derived here and return derived
def main(argv=None):
 initialized_derived = Derived.input_from_text(deque(open("file.txt")))
 assert initialized_derived.val1 is 1
 assert initialized_derived.val2 is 2

Is there a good way to do this? Basically looking for something similar to what you would find in C++ with:

//calls operator>>(Base) then operator>>(Derived)
cin >> initialized_derived;

This way each class is nicely encapsulated and the base/derived classes don't need to know anything about each other (excepting __init__ which knows the number of args base takes).

Answer 1

Just realized that I was going about this the wrong way. Simple fix is to do something like:

class Base:
 def __init__(self):
 pass
 def input_from_text(self, init_deque):
 self.val1 = init_deque.popleft()
class Derived(Base):
 def __init__(self):
 Base.__init__(self)
 def input_from_text(self, init_deque):
 Base.input_from_text(self, init_deque)
 self.val2 = init_deque.popleft()