Python local vs global variables

Question

I understand the concept of local and global variables in Python, but I just have a question about why the error comes out the way it is in the following code. Python execut

Answer 1

This is because, in python, you need to tell that you are going to modify the value of a global variable. You do that as:

def test():
  global a
  print a  #line 4, Error : local variable 'a' referenced before assignment
  a=0      #line 5

With global a, you can modify variables in the function. You may want to have a look at this:

• Python: Why is global needed only on assignment and not on reads?