About variable scope?

Question

I had a math test today and one of the extra credit questions on the test was

product = 1
for i in range(1,7,2):
    print i
    product = product * i
print i
print product

We were supposed to list out the steps of the loop which was easy; but it got me thinking, why does this program run? the second print i seems out of place to me. I would think that the i only exists for the for loop and then get's destroyed so when you call the second print i there is no variable i and you get an error.

Why does i remain a global variable?

Answer 1

Python does not have block scope. Any variables defined in a function are visible from that point only, until the end of the function.

Answer 2

The Devil is in the Details

Naming and binding

A block is a piece of Python program text that is executed as a unit. The following are blocks: a module, a function body, and a class definition.

Or in simple words, a for loop is not a block

A scope defines the visibility of a name within a block. If a local variable is defined in a block, its scope includes that block. If the definition occurs in a function block, the scope extends to any blocks contained within the defining one, unless a contained block introduces a different binding for the name.

So any variable defined is visible from the point of definition to the end of scope of the block, function, module or class definition.

Why does i remain a global variable?

From the nomenclature parlance, I will call i a global variable, if your highlighted code is part of the module rather than a defined function.