How does function scope affect variable behavior?

Function scope affects variable behavior by determining where a variable can be accessed and modified within a program. Here are the key points:

1. Local Variables: Variables defined within a function are local to that function. They cannot be accessed outside of it. For example:

   def my_function():
       x = 10  # Local variable
       print(x)
   
   my_function()  # Outputs: 10
   print(x)  # Raises an error: NameError: name 'x' is not defined

2. Global Variables: Variables defined outside of any function are global and can be accessed from any function within the same module. However, if you want to modify a global variable inside a function, you need to declare it as global:

   x = 10  # Global variable
   
   def modify_global():
       global x
       x = 20  # Modifies the global variable
   
   modify_global()
   print(x)  # Outputs: 20

3. Enclosing Scope: Functions can also access variables from their enclosing scope (like outer functions). This is known as a closure:

   def outer_function(x):
       def inner_function():
           print(f"x from outer function: {x}")
       inner_function()
   
   outer_function(30)  # Outputs: x from outer function: 30

Understanding function scope helps prevent unintended side effects and makes your code more predictable and easier to debug.