On Monday, February 18, 2013 6:09:16 AM UTC-8, John Reid wrote:
> I'm aware how to construct the namedtuple and the tuple. My point was
> that they use different syntaxes for the same operation and this seems
> to break ipython. I was wondering if this is a necessary design feature
> or perhaps just an oversight on the part of the namedtuple author or
> ipython developers.
It was not an oversight on the part of the namedtuple author.
It was a deliberate design decision to improve usability for
named tuple's primary use case.
Consider a namedtuple such as:
Person = namedtuple('Person', ['name', 'rank', 'serial_number'])
With the current signature, instances can be created like this:
p = Person('Guido', 'BDFL', 1)
If instead, the __new__ signature matched that of regular tuples,
you would need to write:
p = Person(('Guido', 'BDFL', 1))
The double parens are awkward. You would lose tooltips that prompt you for
Person(name, rank, serial_number). You would lose the ability to use keyword
arguments such as Person(rank='BDFL', serial_number=1, name='Guido') or
Person(**d). The repr for the namedtuple would lose its eval(repr(t))
roundtrip property.
If your starting point is an existing iterable such as s=['Guido', 'BDFL', 1],
you have a couple of choices: p=Person(*s) or p=Person._make(s). The latter
form was put it to help avoid unpacking and repacking the arguments.
Raymond
--
http://mail.python.org/mailman/listinfo/python-list
