braver schrieb:
Can open two files in a with statement:
with open(src) as readin, open(dst,"w") as writin: # WRONG: comma
doesn't work
...
-- so that you have transactional safety for two file descriptors?
The comma syntax doesn't work, but is there a way, except for
with open(src) as readin:
with open(dst,"w) as writin:
...
I'm not aware of any pre-defined context manager which does that.
But you can write your own context manager to do that, even a
generalized combinator for taking two managers and create one, like this:
with context_creator(open, [src], open, [dst, "w"]) as readin, writin:
...
A fundamental problem though would be that the semantics become
difficult. If closing the "outer" file fails, it's impossible to
"rollback" the inner one.
So I think it really is better to use the nested with, which makes it
crystal clear that the inner block might succeed independently from the
outer one.
Diez
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