#------------------------------------------------------------------------------
# Scope.py
#
# The scope of a variable is the area of the program where it can be accessed,
# i.e. read from or written to.
#
# The three different different x's in different parts of the program represent
# different areas of memory, i.e. there are 3 different variables all with the
# name x. The one in main is called the 'global' variable x.
#
# In Python, functions cannot write to global variables, by say assigning a 
# value to them. A function can read from a global variable though, for instance
# by printing it. In general, your functions should not interact with global 
# variables in any way, since it can make the job of tracing your program very
# complex, leading to confusion and errors.
#
#------------------------------------------------------------------------------

# Try putting x = 8 here, you'll find no difference.  Thus,  the "main program" 
# is really everything outside of all functions.


def fcn1():
   x = 6      # A local variable called x, different from that in fcn2() and 
   print(x)   # in the "main program". It's scope is fcn1() only.
# end fcn1()

def fcn2():
   x = 7      # Another local variable called x. Try commenting this line out.
   print(x)   # Then there is no local x, and so the global x is printed.
# end fcn2()


#------------------------------------------------------------------------------
# no function main(), so this is global scope

x = 8         # Another variable called x in the global scope, i.e outside
              # of all functions. 
print(x)
fcn1()
print(x)
fcn2()
print(x)