默认字典(defaultdict)
defaultdict是对字典的类型的补充,它默认给字典的值设置了一个类型。
1、创建默认字典
import collections dic = collections.defaultdict(list) # 设置dic的值类型为list dic['k1'].append('evescn')
2、查看默认字典
print(dic) 输出结果: defaultdict(<class 'list'>, {'k1': ['evescn']})
3、查看默认字典的方法
>>> dir(dic) ['__class__', '__contains__', '__copy__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__missing__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'clear', 'copy', 'default_factory', 'fromkeys', 'get', 'items', 'keys', 'pop', 'popitem', 'setdefault', 'update', 'values']
class defaultdict(dict): """ defaultdict(default_factory[, ...]) --> dict with default factory The default factory is called without arguments to produce a new value when a key is not present, in __getitem__ only. A defaultdict compares equal to a dict with the same items. All remaining arguments are treated the same as if they were passed to the dict constructor, including keyword arguments. """ def copy(self): # real signature unknown; restored from __doc__ """ D.copy() -> a shallow copy of D. """ pass def __copy__(self, *args, **kwargs): # real signature unknown """ D.copy() -> a shallow copy of D. """ pass def __getattribute__(self, name): # real signature unknown; restored from __doc__ """ x.__getattribute__('name') <==> x.name """ pass def __init__(self, default_factory=None, **kwargs): # known case of _collections.defaultdict.__init__ """ defaultdict(default_factory[, ...]) --> dict with default factory The default factory is called without arguments to produce a new value when a key is not present, in __getitem__ only. A defaultdict compares equal to a dict with the same items. All remaining arguments are treated the same as if they were passed to the dict constructor, including keyword arguments. # (copied from class doc) """ pass def __missing__(self, key): # real signature unknown; restored from __doc__ """ __missing__(key) # Called by __getitem__ for missing key; pseudo-code: if self.default_factory is None: raise KeyError((key,)) self[key] = value = self.default_factory() return value """ pass def __reduce__(self, *args, **kwargs): # real signature unknown """ Return state information for pickling. """ pass def __repr__(self): # real signature unknown; restored from __doc__ """ x.__repr__() <==> repr(x) """ pass default_factory = property(lambda self: object(), lambda self, v: None, lambda self: None) # default """Factory for default value called by __missing__()."""
4、练习
有如下值集合 [11,22,33,44,55,66,77,88,99,90...], 将所有大于 66 的值保存至字典的第一个key中, 将小于 66 的值保存至第二个key的值中。 即: {'k1': 大于66 , 'k2': 小于66}
# 原生字典
values = [11, 22, 33,44,55,66,77,88,99,90] my_dict = {} for value in values: if value>66: if my_dict.has_key('k1'): my_dict['k1'].append(value) else: my_dict['k1'] = [value] else: if my_dict.has_key('k2'): my_dict['k2'].append(value) else: my_dict['k2'] = [value]
# 默认字典 from collections import defaultdict values = [11, 22, 33,44,55,66,77,88,99,90] my_dict = defaultdict(list) for value in values: if value>66: my_dict['k1'].append(value) else: my_dict['k2'].append(value) defaultdict字典解决方法