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Sometimes, we want to modify a global name from within a local scope. How do we go about doing this?

global_var = 10

def some_function():
  global_var = 20

some_function()

print(global_var)

The output would be:

In the above example, the value of global_var remains 10 because global_var = 20 is in a local scope.

Similar to the nonlocal statement, Python provides the global statement to allow the modification of global names from a local scope.

global_var = 10

def some_function():
  global global_var
  global_var = 20

some_function()

print(global_var)

The output would now be:

In addition, the global statement can be used even if the name has not been defined in the global namespace. Using the global statement would create the new variable in the global namespace.

def some_function():
  global x
  x = 30

some_function()
print(x)

This would output:

In summary, the global keyword is used within a local scope to associate a variable name with a name in the global namespace. This association is only valid within the local scope global is used.

Instructions

This exercise starts the same as the last with paint_gallons_available declared inside the local scope of the function, print_available(). The difference now is that paint_gallons_available is now being accessed by a for loop in the global scope. This will result in an error.

Run the code to confirm the NameError on paint_gallons_available.

Associate the paint_gallons_available declaration to the global namespace by adding a line to the top of the print_available() function.

This will allow paint_gallons_available to be used within the global scope and no NameError will occur.

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