`from sys import path` in `compile` in a local function raises `NameError`

[lionelkusch]

Bug report

Bug description:

function = True
if function:
    def run_example():
        code = """
from sys import path
    
def function():
    print(path)
    
function()
        """
        # Compile the code
        compiled_code = compile(code, 'test_function.py', 'exec')

        # Execute the compiled code
        exec(compiled_code)
    run_example()
else:
    # Read the file
    code = """
from sys import path
    
def function():
    print(path)
    
function()
    """
    # Compile the code
    compiled_code = compile(code, 'test_function.py', 'exec')

    # Execute the compiled code
    exec(compiled_code)

When the boolean is true, I get this error:

Traceback (most recent call last):
  File ".../error_import.py", line 17, in <module>
    run_example()
    ~~~~~~~~~~~^^
  File ".../error_import.py", line 16, in run_example
    exec(compiled_code)
    ~~~~^^^^^^^^^^^^^^^
  File "test_function.py", line 7, in <module>
    def function():
    ^^^^^^^^^^
  File "test_function.py", line 5, in function
    from sys import path
              ^^^^
NameError: name 'path' is not defined

If the boolean is false, I didn't get any error.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

[gaogaotiantian]

This is caused by closure. I agree this is not super ideal, but not sure if it's a bug (or if we could fix it easily).

The root problem is from sys import path stores path with STORE_NAME, but trying to read path in a function uses LOAD_GLOBAL. When you exec this in a function scope, STORE_NAME will store path to local variables, instead of global variables.

If you think about it, what you are trying to do is

def run_example():
    from sys import path
    
    def function():
        print(path)
    
    function()

It requires function knowing path is a closure variable (free variable) - but that's impossible when you compile

from sys import path

def function():
    print(path)
    
function()

Actually, this is a very difficult problem to solve. pdb needs this to work, and a lot of effort was made to make it work (in most cases).

In your specific example, do a exec(compiled_code, globals()) would do, but I'm not sure if that's acceptable in your case.

To summarize, unfortunate, but I don't believe this is a bug. It has been like this for a really long time and it's not trivial to make it work as (you) expected.

[lionelkusch]

Yes, indeed, it's not a bug, it's just that the error was misleading me.
I didn't take the time to read the documentation of exec and I was not aware of the difference between STORE_NAME and LOAD_GLOBAL.
In my case, your proposition of using global parameter of exec will work for me. Thank you.

[gaogaotiantian]

Glad that it worked for you with globals. I'll close this issue then.