def foo(var1, var2):
    print("in function foo: var1 =", var1)
    print("in function foo: var2 =", var2, "\n")


var1 = "hello"
var2 = "goodbye"
var3 = "earth"
var4 = "moon"

print("before calling foo: var1 =", var1)
print("before calling foo: var2 =", var2, "\n")

foo(var3, var4)

print("after calling foo: var1 =", var1)
print("after calling foo: var2 =", var2, "\n")