> print(child_pid) # child_pid is undefined

Why on earth would it be undefined?

Indeed, users would expect the new uses of "as" to behave as the previous ones. The problem is that "with" and "except" do things differently:

In [1]: import os

In [2]: with open(os.path.expanduser('~/tmp/xx')) as f:

   ...: pass

   ...:

In [3]: print(f)

<_io.TextIOWrapper name='/Users/apalala/tmp/xx' mode='r' encoding='UTF-8'>

In [4]: try:

   ...: print('ok')

   ...: raise Exception()

   ...: except Exception as e:

   ...: pass

   ...:

In [5]: print(e)
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-5-bb2ea196f768> in <module>()
----> 1 print(e)

NameError: name 'e' is not defined

Anyway, if you want to propose an alternative to PEP 572, you ought to
write your own competing PEP.

I don't take that as a challenge. It would be good to have different, maybe somewhat competing PEPs. It's been done before.

Juancarlo Añez