Declaring variables inside a function python

Question

For some reason I keep getting error in my code stating that my variables have not been declared. This only happens when I try to declare them in a function and not outside.

example

x, y = 105,107 
print (x,y) 

the above line of code works and gives me the output 105 107

but when I do this below

def fun1():
  x, y = 105,107 
print (x,y) 

I get NameError: name 'x' is not defined

need help to understand what's happening.

Answer 1

One of the main utilities of functions is exactly the way they allow one to isolate variables - no worries about clashing names for the code in various functions - once a function works properly, it is done.

But if one needs to expose variables that populated inside functions to the outside world, it is possible with the keyword "global". Notice that this is in general considered bad practice, and even for small scripts, there are often better solutions. But, common sense should always be the rule:

def fun1():
   global x, y
   x, y = 105, 107

fun1()
print(x, y)

Note that your code had another incorrect assumption: code inside function bodies is not executed unless the function is called - so, in the example in your question, even if you had declared the variables as global, the print call would still raise the same error, since you are not executing the line that defines these variables by calling the function.

Now, you've learned about "globals" - next step is forget it exists and learn how to work with variables properly encapsulated inside functions, and when you get to some intermediate/advanced level, then you will be able to judge when "globals" might actually do more good than harm (which is almost never).