I know Guido is on record as not wanting to allow both "for name in sequence" and "for name = expr" due to that being a very subtle distinction between iteration and simple assignment (especially given that Julia uses them as alternate spellings for the same thing), but I'm wondering if it may be worth considering such a distinction in *with statements*, such that we allowed "with name = expr" in addition to "with cm as name" (where "name = expr" is just an ordinary assignment statement that doesn't trigger the context management protocol).
The related enhancement to comprehensions would then be to allow with clauses to be interleaved between the for loops and the if statements, such that you could write things like:
pairs = [(f(y), g(y)) for x in things with y = h(x)] contents = [f.read() for fname in filenames with open(fname) as f]
while still preserving the property where comprehensions can be correctly interpreted just by converting each of the clauses to the corresponding statement form.
Even without the "with name = expr" change, allowing with clauses in comprehensions would let you do (by way of a suitably defined "bind" CM):
pairs = [(f(y), g(y)) for x in things with bind(h(x)) as y]
Including standard "with open(...) as f" context management in list comprehensions would also be a good idea, I think it's in the same idea as including : allowing both statements (imperative programming) and list comprehension (more "functional"). The same story goes for exceptions :
for x in range(5): try: yield f(x) except Exception: yield 0
isn't "refactorable" as a list comprehension like :
[try f(i) except Exception: 0 for x in range(5)]
But I think that would cover another subject :)
But if the "with =" syntax is accepted for simple assignment, it could indeed introduce a confusion compared to the "with as" in context management, and having a complete different keyword (or punctuation) is maybe be better.
As a symmetry, we could also introduce the "with =" syntax in normal statement :P that'd do a normal assignement, although that's be probably stupid because normal assignements works well.