先看演示
像类一样的访问属性
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from collections import namedtupleFriend = namedtuple('Friend', ['name', 'gender', 'address', 'star', 'signature'])RidingRoad = Friend('RidingRoad', 'male', 'Mars', 'The five-star high praise', 'Change the world by Program!\n' 'Do what you like!\n' 'Live what you want!')print(RidingRoad.name)print(RidingRoad.gender)print(RidingRoad.address)print(RidingRoad.star)print(RidingRoad.signature) |
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RidingRoadmaleMarsThe five-star high praiseChange the world by Program!Do what you like!Live what you want! |
类似字典的访问
像字典一样访问items、keys、values
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for key, value in RidingRoad.__dict__.items(): print(key, value)print("*" * 30)for key in RidingRoad.__dict__.keys(): print('{}: '.format(key), eval('RidingRoad.{}'.format(key)))print("*" * 30)for value in RidingRoad.__dict__.values(): print(value) |
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('name', 'RidingRoad')('gender', 'male')('address', 'Mars')('star', 'The five-star high praise')('signature', 'Change the world by Program!\nDo what you like!\nLive what you want!')******************************('name: ', 'RidingRoad')('gender: ', 'male')('address: ', 'Mars')('star: ', 'The five-star high praise')('signature: ', 'Change the world by Program!\nDo what you like!\nLive what you want!')******************************RidingRoadmaleMarsThe five-star high praiseChange the world by Program!Do what you like!Live what you want! |
为什么可以这样？
到这里，你应该会有两个疑问：
- 为什么有类的影子？
- 为什么有字典的影子？
源码解析
为什么有类的影子？
看源码的_class_template部分，其实函数内部为我们创了一个类了
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# Fill-in the class template class_definition = _class_template.format( typename = typename, field_names = tuple(field_names), num_fields = len(field_names), arg_list = repr(tuple(field_names)).replace("'", "")[1:-1], repr_fmt = ', '.join(_repr_template.format(name=name) for name in field_names), field_defs = '\n'.join(_field_template.format(index=index, name=name) for index, name in enumerate(field_names)) ) if verbose: print class_definition |
然后_class_template干了什么？对类进行定义
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_class_template = '''\class {typename}(tuple): '{typename}({arg_list})' __slots__ = () _fields = {field_names!r} def __new__(_cls, {arg_list}): 'Create new instance of {typename}({arg_list})' return _tuple.__new__(_cls, ({arg_list})) @classmethod def _make(cls, iterable, new=tuple.__new__, len=len): 'Make a new {typename} object from a sequence or iterable' result = new(cls, iterable) if len(result) != {num_fields:d}: raise TypeError('Expected {num_fields:d} arguments, got %d' % len(result)) return result def __repr__(self): 'Return a nicely formatted representation string' return '{typename}({repr_fmt})' % self def _asdict(self): 'Return a new OrderedDict which maps field names to their values' return OrderedDict(zip(self._fields, self)) def _replace(_self, **kwds): 'Return a new {typename} object replacing specified fields with new values' result = _self._make(map(kwds.pop, {field_names!r}, _self)) if kwds: raise ValueError('Got unexpected field names: %r' % kwds.keys()) return result def __getnewargs__(self): 'Return self as a plain tuple. Used by copy and pickle.' return tuple(self) __dict__ = _property(_asdict) def __getstate__(self): 'Exclude the OrderedDict from pickling' pass{field_defs}''' |
为什么有字典的影子？
看源码的 _asdict部分，这里封装成了有序字典，所以我们可以通过__dict__访问字典的特性了
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__dict__ = _property(_asdict) def _asdict(self): 'Return a new OrderedDict which maps field names to their values' return OrderedDict(zip(self._fields, self)) |
以上就是python namedtuple函数的使用的详细内容，更多关于python namedtuple函数的资料请关注服务器之家其它相关文章！
原文链接：https://juejin.cn/post/6973302732740362277
