[Tutor] How to reuse code in Python

[Negroup -]

Hi.
Suppose that I need to use in my project a module that belongs to
another project, because - with some tuning - it can fit my needings.

This is what I mean, with an example:

module.py
limit = 30

class A:
  def __init__(self):
    self.num = 20
  def info(self):
    return limit
  def inc_num(self):
    self.num += 1
  def check(self):
    return self.num > limit

Now suppose that I'd like to have the same class A in my module, but
also I want that the initial value of limit is set to 25.

>>> limit = 25
>>> from module import A
>>> a = A()
>>> a.info()
30

Now I have a couple of questions.
The most important: how to reuse the class A in my module? "class A"
is not short and I think that copy/paste, then apply changes, wouldn't
be a valid solution!

This is the second question, more for curiosity than for real necessity, anyway:

Considering that:
>>> limit # Obvious
25

>>> print a.limit # Obvious
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: A instance has no attribute 'limit'

>>> print A.limit # Obvious
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: class A has no attribute 'limit'

where is the value 30 coming from?

Thanks, dear tutors!