this code is ok
def test(t):
	n = 0
	def f(t):
		print(t+str(N))
	f(t)	
test('test')
but this code have error

def test(t):
	n = 0
	def f(t):
		n = n+1
		print(t+str(n))
	f(t)	
test('test')	

we can fix this by edit code to:

def test(t):
	n = 0
	def f(t):
		N = n+1
		print(t+str(N))
	f(t)	
test('test')

This tracker is for issues related to CPython. The examples presented in the report look more like user error with variables where N is not defined in the first examples. Can you please illustrate over the examples over how this is an issue with interpreter and the changes you are proposing?

This is intended behavior.

When a variable has an assignment anywhere in a function, it becomes a local. Once a local variable exists, it will shadow the non-local variable.

So by having the "n =", you are marking "n" as a local variable. When the "n + 1" tries to read the local, it has not yet been set, so it fails.

If you want to read and write to "n" in the outer function, you will need the nonlocal statement - https://docs.python.org/3/reference/simple_stmts.html#the-nonlocal-statement