在namedtuple中typename的相关性

Question

from collections import namedtuple

Point = namedtuple('whatsmypurpose',['x','y'])
p = Point(11,22)
print(p)

输出:

whatsmypurpose(x=11,y=22)

什么是相关性/用途'whatsmypurpose'？

Answer 1

namedtuple()是tuple子类的工厂函数.这'whatsmypurpose'是类型名称.创建命名元组时,whatsmypurpose会在内部创建具有此名称()的类.

您可以通过使用详细参数来注意这一点:

Point=namedtuple('whatsmypurpose',['x','y'], verbose=True)

您也可以尝试type(p)验证这一点.

Answer 2

'whatsmypurpose'为新子类赋予其类型名称.来自文档:

collections.namedtuple(typename,field_names,verbose = False,rename = False)
返回名为typename的新元组子类.

这是一个例子:

>>> 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)
>>> 

将verbose参数设置为True,您可以查看完整的whatsmypurpose类定义.

>>> 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')