NameError when the variable exists - code execution

Python
1

Hi there,
I’m quite new to Python and I have some doubts on how the code execution works.
For example, if I have:

letters = [“a”, “b”, “c”]
print(letters)

if I run the two lines separately on VS code, then for the second line I get the NameError: name ‘letters’ is not defined.

Schermata 2022-09-06 alle 16.40.52
Schermata 2022-09-06 alle 16.40.522038×446 68.6 KB

On the contrary, running the two lines together does not imply any problem.
But if letters is defined/assigned in the first line, then why running the two lines separate create a problem?

Thanks and sorry in advance if it sounds a “stupid question”.

2

What do you mean by “run the two lines separately”?

If you try to use a variable that does not exist, you should get that error. For example:

print(any_variable_that_does_not_exist)

It would also apply if you used the variable anywhere else:

new_variable = any_variable_that_does_not_exist + 2
3

Thanks for the reply.
I mean literally run only the first line of code

letters = [“a”, “b”, “c”]

and then run only

print(letters)

I may be biased from R where if I firstly define letters (run only first line) and then run only the print command, it shows me the desired output.
Hope it is clearer now.

4

Yes, but what do you mean by “only run”. Are you commenting out the other line? Are you using some special “run selected” function? I do not think any state is retained between runs if that is the case.

If you ran the lines one at a time in the Python REPL it should work just fine.

5

No, without commenting out the other line.
Just selecting the first and execute (control+otion+n) and then doing the same with the second one.

I just realize that if I run it in the interactive window in VS code, it works as expected. So it may be the way of execution (shift+enter) vs (control+otion+n)?

Thanks again

6

Yep, I think the way you executed it just makes completely isolated environments where the second run is not aware of the first one.

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