Newbie question, Does variable need instance after its class modification?

[chenyu]

Hello everyone,
I am newbie to python programming, then read other's code and try to
modify for study. My question is as follows:
1. class name is "class1", it has one method "method1" and the class
is in the file "class1.py".
2. In the "pythonwin interactive window":
  2.1  c1 = class1()
  2.2  cl.method1()
3. Because I found there is problem in the method1(), therefore I
modify it by adding "print" statement for debugging in the file
"class1.py"
4. In the "pythonwin interactive window", 
  4.1 c1.method1()
   special ERROR message is given.
5. In the "pythonwin interactive window", 
  5.1  c1 = class1()
  5.2  cl.method1()
  The error message disappear, and my debugging information is given.

Does it mean that if I modify one file, any variable which instanced
object from the file is useless and should be instanced again. Is it
right?



Thank you in advance.
kind regards/chenyu