contexter 0.1.3

Replacing contextlib.nested [2]

You can use Contexter(*managers) as a drop-in replacement for contextlib.nested(*managers), just without the confusing error prone quirks mentioned in the official documentation.

Replacing contextlib.closing [3]

Just forget about it. Contexter turns close-able objects into context managers automatically.

Replacing contextlib.ExitStack [4]

Contexter offeres everything contextlib.ExitStack does (and more). If you want a drop-in replacement that also works for Python 2.x and 3.2, you can use our backported ExitStack, a subclass of Contexter that is API compatible to the contextlib variant.

Replacing everything else from contextlib

If you really want to stick with the standard API, you can. Contexter implements all public APIs from contextlib and backports new features as soon as they are introduced.

More examples:

Contexter keeps track of the results of all invoked context managers. You can access the results later and don’t have to unpack them all at the beginning.

with Contexter(open('a.txt'), open('b.txt', 'w')) as ctx:
    in_file, out_file = ctx.values()
    assert ctx.value(0) is in_file
    assert ctx[0] is in_file
    assert ctx[0:2] == [in_file, out_file]
    assert len(ctx) == 2

If you don’t like the << syntax, there is a method that does the same.

with Contexter() as ctx:
    in_file = ctx << open('a.txt')
    out_file = ctx.append(open('b.txt', 'w'))

Contexter contexts are nestable. Each level of nesting maintains its own stack of context managers and result values. This allows you to control the lifetime of contexts very precisely.

with Contexter() as ctx:
    out_file = ctx << open('b.txt', 'w')

    with ctx:
        in_file = ctx << open('a.txt')
        copy_data(in_file, out_file)

    assert in_file.closed == True
    assert out_file.closed == False

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