Relevance of typename in namedtuple
'whatsmypurpose'
gives the new subclass its type name. From the docs:
collections.namedtuple(typename, field_names, verbose=False,rename=False)
Returns a new tuple subclass named typename.
Here is an example:
>>> from collections import namedtuple
>>> Foo = namedtuple('Foo', ['a', 'b'])
>>> type(Foo)
<class 'type'>
>>> a = Foo(a = 1, b = 2)
>>> a
Foo(a=1, b=2)
>>> Foo = namedtuple('whatsmypurpose', ['a', 'b'])
>>> a = Foo(a = 1, b = 2)
>>> a
whatsmypurpose(a=1, b=2)
>>>
Set the verbose
parameter to True
and you can see the complete whatsmypurpose
class definition.
>>> Foo = namedtuple('whatsmypurpose', ['a', 'b'], verbose=True)
from builtins import property as _property, tuple as _tuple
from operator import itemgetter as _itemgetter
from collections import OrderedDict
class whatsmypurpose(tuple):
'whatsmypurpose(a, b)'
__slots__ = ()
_fields = ('a', 'b')
def __new__(_cls, a, b):
'Create new instance of whatsmypurpose(a, b)'
return _tuple.__new__(_cls, (a, b))
@classmethod
def _make(cls, iterable, new=tuple.__new__, len=len):
'Make a new whatsmypurpose object from a sequence or iterable'
result = new(cls, iterable)
if len(result) != 2:
raise TypeError('Expected 2 arguments, got %d' % len(result))
return result
def _replace(_self, **kwds):
'Return a new whatsmypurpose object replacing specified fields with new values'
result = _self._make(map(kwds.pop, ('a', 'b'), _self))
if kwds:
raise ValueError('Got unexpected field names: %r' % list(kwds))
return result
def __repr__(self):
'Return a nicely formatted representation string'
return self.__class__.__name__ + '(a=%r, b=%r)' % self
def _asdict(self):
'Return a new OrderedDict which maps field names to their values.'
return OrderedDict(zip(self._fields, self))
def __getnewargs__(self):
'Return self as a plain tuple. Used by copy and pickle.'
return tuple(self)
a = _property(_itemgetter(0), doc='Alias for field number 0')
b = _property(_itemgetter(1), doc='Alias for field number 1')
namedtuple()
is a factory function for tuple
subclasses. Here, 'whatsmypurpose'
is the type name. When you create a named tuple, a class with this name (whatsmypurpose
) gets created internally.
You can notice this by using the verbose argument like:
Point=namedtuple('whatsmypurpose',['x','y'], verbose=True)
Also you can try type(p)
to verify this.