[Python-Dev] Multiline with statement line continuation (original) (raw)

Allen Li cyberdupo56 at gmail.com
Tue Aug 12 01:08:00 CEST 2014

This is a problem I sometimes run into when working with a lot of files simultaneously, where I need three or more with statements:

with open('foo') as foo:
    with open('bar') as bar:
        with open('baz') as baz:
            pass

Thankfully, support for multiple items was added in 3.1:

with open('foo') as foo, open('bar') as bar, open('baz') as baz:
    pass

However, this begs the need for a multiline form, especially when working with three or more items:

with open('foo') as foo, \
     open('bar') as bar, \
     open('baz') as baz, \
     open('spam') as spam \
     open('eggs') as eggs:
    pass

Currently, this works with explicit line continuation, but as all style guides favor implicit line continuation over explicit, it would be nice if you could do the following:

with (open('foo') as foo,
      open('bar') as bar,
      open('baz') as baz,
      open('spam') as spam,
      open('eggs') as eggs):
    pass

Currently, this is a syntax error, since the language specification for with is

with_stmt ::=  "with" with_item ("," with_item)* ":" suite
with_item ::=  expression ["as" target]

as opposed to something like

with_stmt ::=  "with" with_expr ":" suite
with_expr ::=  with_item ("," with_item)*
          |    '(' with_item ("," with_item)* ')'

This is really just a style issue, furthermore a style issue that requires a change to the languagee grammar (probably, someone who knows for sure please confirm), so at first I thought it wasn't worth mentioning, but I'd like to hear what everyone else thinks. -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 473 bytes Desc: not available URL: <http://mail.python.org/pipermail/python-dev/attachments/20140811/0cd007b3/attachment.sig>

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