In article
<fe3354e50905151817ie4df792hebec03ae42eca...@mail.gmail.com>,
Sam Tregar <s...@tregar.com> wrote:
> Can anyone explain why this creates a list containing a
> dictionary:
> [{'a': 'b', 'foo': 'bar'}]
> But this creates a list of keys of the dictionary:
> list({ "a": "b", "foo": "bar" })
The first example is a list, expressed as a list display literal,
containing one object: a dictionary, expressed as a dictionary display
literal.
<http://docs.python.org/reference/expressions.html#atoms>
The second example is a call to the built-in function "list", which
takes a single iterable as an argument and returns "a list whose items
are the same and in the same order as iterableĀs items". In this case,
that single argument is a dictionary. In an iteration context, the
iterator obtained for a dictionary iterates over the dictionary's keys.
The second example is essentially shorthand for:
list({ "a": "b", "foo": "bar" }.iterkeys())
<http://docs.python.org/library/functions.html#list>
<http://docs.python.org/library/stdtypes.html#mapping-types-dict>
--
Ned Deily,
n...@acm.org
--
http://mail.python.org/mailman/listinfo/python-list
