Split multiple same-level context managers to multiple lines in Python

Question

I know that the with statement supports multiple context managers on the same level, like so:

with open('foo.txt') as foo, open('bar.txt') as bar:
    do_something()

But what if the list of context managers is getting too long for a single line? e.g.:

with open('foo.txt') as foo, open('bar.txt') as bar, open('bla.txt') as bla, open('yada.txt') as yada:
    do_something()

Currently, these are invalid syntax in Python 3.7:

with (
    open('foo.txt') as foo,
    open('bar.txt') as bar,
    open('bla.txt') as bla,
    open('yada.txt') as yada, # same thing without the last trailing comma
):
    do_something()

with 
    open('foo.txt') as foo,
    open('bar.txt') as bar,
    open('bla.txt') as bla,
    open('yada.txt') as yada, # same thing without the last trailing comma
:
    do_something()

I could do:

foo = open('foo.txt')
bar = open('bar.txt')
bla = open('bla.txt')
yada = open('yada.txt')

with foo, bar, bla, yada:
    do_something()

But even THAT could grow too long as I add more context managers.

I could also do:

with open('foo.txt') as foo:
    with open('bar.txt' as bar:
        with open('bla.txt' as bla:
            with open('yada.txt') as yada:
                do_something()

But it's ugly. It also lacks semantic hints for the human reader. There's a reason why we would want to put multiple context managers on the same level in the first place.

I know it's very uncommon for many context managers to belong to the same level, but it's definitely a possibility.

how about https://stackoverflow.com/questions/3024925/create-a-with-block-on-several-context-managers does this help you? — Devesh Kumar Singh, Jun 13 '19 at 05:03
Possible duplicate of [Create a "with" block on several context managers?](https://stackoverflow.com/questions/3024925/create-a-with-block-on-several-context-managers) — Azat Ibrakov, Jun 13 '19 at 05:36
Using `ExitStack` seems like the cleanest solution, although it does mean extra setup lines. — Kal, Jun 14 '19 at 02:12

ig0774 · Accepted Answer · 2019-06-13T05:27:42.267

1

Line continuations are your friend here...

with \
    open('foo.txt') as foo, \
    open('bar.txt') as bar, \
    open('bla.txt') as bla, \
    open('yada.txt') as yada \
:
    do_something()

This is actually specifically mentioned in PEP-8.

edited Jun 13 '19 at 05:27

answered Jun 13 '19 at 05:19

ig0774

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I'm going to mark this as the answer for now. It seems like a good compromise between the cleanest solution (using `ExitStack`) and convenience (no need for extra setup lines). – Kal Jun 14 '19 at 02:13

Split multiple same-level context managers to multiple lines in Python

1 Answers1