3. Blueprint

The package ‘namedtupledefs’ provides a patched version of the collections.namedtuple with field defaults for namedtuple. This is a drop-in compatible patch with minimal changes only - basically one line in the class template only.

Just use:

import namedtupledefs

Point0 = namedtupledefs.namedtuple('Point', ('x', 'y', 'z'))
Point1 = namedtupledefs.namedtuple('Point', ('x y z'))

point0 = Point0(11, 22, 33)
point1 = Point1(11, 22, 33)

the same with defaults:

from namedtupledefs import namedtuple

Point0defs = namedtupledefs.namedtuple('Point0', ('x', 'y', 'z'), fielddefaults=(22, 33))
Point1defs = namedtupledefs.namedtuple('Point1', ('x y z'), fielddefaults=(22, 33))

point0defs = Point0(11, 22)
point1defs = Point1(11)

with the identical results:

point0defs == point0
point1defs == point1

of the printout:

>>> point0
Point0(x=11, y=22, z=33)

>>> point0defs
Point0(x=11, y=22, z=33)

>>> point1
Point1(x=11, y=22, z=33)

>>> point1defs
Point1(x=11, y=22, z=33)

For merging multiple namedtuple results into one of type named tuple:

>>> point0
Point0(a=11, b=22, c=33)

>>> point1
Point1(d=44, e=55)

>>> point2
Point1(f=66)

>>> psum = point0._merge('PointSum', point1, point2)
PointSum(a=11, b=22, c=33, d=44, e=55, f=66)

The next example shows the assembly of a URL which is processed into seperate parts, and finally concatenated into one named tuple.

# example: RFC3986 - 3. Syntax Components
Scheme = namedtuple('Scheme', ('scheme',), fielddefaults=('https',), verbose=True)
HierPart = namedtuple('HierPart', ('authority', 'path'), fielddefaults=('', '/'))
Query = namedtuple('Query', ('name', ), fielddefaults=('ferret',))
Fragment = namedtuple('Fragment', ('f0', ), fielddefaults=('nose',))


scheme = Scheme()
self.assertEqual(scheme, ('https',))

hier_part = HierPart('example.com:8042', '/over/there', )
self.assertEqual(hier_part, ('example.com:8042', '/over/there', ))

query = Query('ferret',)
self.assertEqual(query, ('ferret',))

fragment = Fragment()
self.assertEqual(fragment, ('nose',))

url = scheme._merge('MyURI', hier_part, query, fragment)
self.assertEqual(
   url,
   ('https', 'example.com:8042', '/over/there', 'ferret', 'nose',)
)
self.assertEqual(url.__class__.__name__, 'MyURI')

See doc-string for more examples.

The contained interfaces are:

• namedtupledefs.namedtuple:

  The drop-in replacement of collections.namedtuple with optional default values.

For the standard library collections.namedtuple see Python documentation [namedtuple].