Ah yes, I see what you mean:
x = 1
print (x) # Prints 1
print([x+i for i in range(1,3)]) # NameError (x)
Anyway, I apologise for posting to Python-Dev on was a known
issue, and turned out to be more me asking for help with
development with Python, rather than development of Python. (My
original use case was a scripting language that could contain
embedded Python code). Thanks to Nick for his original answer.
On Mon, Jun 11, 2018 at 3:10 PM Rob Cliffe via Python-Dev <firstname.lastname@example.org> wrote:
Skip, I think you have misunderstood the point I was making. It was
not whether the loop variable should leak out of a list comprehension.
Rather, it was whether a local variable should, so to speak, "leak into"
a list comprehension. And the answer is: it depends on whether the code
is executed normally, or via exec/eval. Example:
x = 1
print([x+i for i in range(1,3)]) # Prints [2,3]
exec('print([x+i for i in range(1,3)])') # Raises NameError (x)
I (at least at first) found the difference in behaviour surprising.
Change 'def' to 'class' and run it again. You'll be even more surprised.