New submission from Vito De Tullio <[email protected]>:
The enhancement is to add a __init__ method to both contextlib.ExitStack and
contextlib.AsyncExitStack, so that you can pass (async)context managers
directly in the costructor.
additionally, a new "context_managers" / "async_context_managers" field is
added to retrieve the values passed
This will ease the usage with lists of context managers
instead of:
with ExitStack() as stack:
files = [stack.enter_context(open(fname)) for fname in filenames]
you can have
with ExitStack(*(open(fname) for fname in filenames)) as stack:
files = stack.context_managers
In my use case I have a fixed + variable number of (async)context managers, and
I don't even need the "as" part
...
in_send, in_receive = trio.open_memory_channel(0)
out_sends, out_receives = [], []
for _ in range(n): # n is dynamic
out_send, out_receive = trio.open_memory_channel(0)
out_sends.append(out_send)
out_receives.append(out_receive)
# syntax error
async with in_send, in_receive, *out_sends, *out_receives:
...
# with current AsyncExitStack
async with AsyncExitStack() as stack:
await stack.async_context_managers(in_send)
await stack.async_context_managers(in_receive)
for out_send in out_sends:
await stack.async_context_managers(out_send)
for out_receive in out_receives:
await stack.async_context_managers(out_receives)
...
# with the change
async with AsyncExitStack(in_send, in_receive, *out_sends, *out_receives):
...
----------
components: Library (Lib)
messages: 381561
nosy: ZeD
priority: normal
severity: normal
status: open
title: add constructor that support multiple context managers to
contextlib.ExitStack and contextlib.AsyncExitStack
type: enhancement
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Python tracker <[email protected]>
<https://bugs.python.org/issue42424>
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