脚本宝典收集整理的这篇文章主要介绍了python namedtuple函数的使用,脚本宝典觉得挺不错的,现在分享给大家,也给大家做个参考。
From collections import namedtuple Friend = 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)
RidingRoad male Mars The five-star high praise Change the world by Program! Do what you like! Live what you want!
像字典一样访问ITems、keys、values
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)
('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!') ****************************** RidingRoad male Mars The five-star high praise Change the world by Program! Do what you like! Live what you want!
到这里,你应该会有两个疑问:
看源码的_class_template部分,其实函数内部为我们创了一个类了
# 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
_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} '''
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
__dict__ = _property(_asdict) def _asdict(self): 'Return a new OrderedDict which maps field names to their values' return OrderedDict(zip(self._fields, self))
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