我有一个大字典对象，它有几个键值对(大约16个)，但我只对其中3个感兴趣。将这样的字典子集化的最佳方法(最短/有效/最优雅)是什么?
我知道的最好的是:
bigdict = {'a':1,'b':2,....,'z':26}
subdict = {'l':bigdict['l'], 'm':bigdict['m'], 'n':bigdict['n']}
我相信有比这更优雅的方式。
当前回答
还有一个问题(我更喜欢Mark Longair的答案)
di = {'a':1,'b':2,'c':3}
req = ['a','c','w']
dict([i for i in di.iteritems() if i[0] in di and i[0] in req])
其他回答
可能:
subdict=dict([(x,bigdict[x]) for x in ['l', 'm', 'n']])
Python 3甚至支持以下内容:
subdict={a:bigdict[a] for a in ['l','m','n']}
注意你可以在字典中检查是否存在，如下所示:
subdict=dict([(x,bigdict[x]) for x in ['l', 'm', 'n'] if x in bigdict])
分别地。对于python 3
subdict={a:bigdict[a] for a in ['l','m','n'] if a in bigdict}
解决方案
from operator import itemgetter
from typing import List, Dict, Union
def subdict(d: Union[Dict, List], columns: List[str]) -> Union[Dict, List[Dict]]:
"""Return a dict or list of dicts with subset of
columns from the d argument.
"""
getter = itemgetter(*columns)
if isinstance(d, list):
result = []
for subset in map(getter, d):
record = dict(zip(columns, subset))
result.append(record)
return result
elif isinstance(d, dict):
return dict(zip(columns, getter(d)))
raise ValueError('Unsupported type for `d`')
使用实例
# pure dict
d = dict(a=1, b=2, c=3)
print(subdict(d, ['a', 'c']))
>>> In [5]: {'a': 1, 'c': 3}
# list of dicts
d = [
dict(a=1, b=2, c=3),
dict(a=2, b=4, c=6),
dict(a=4, b=8, c=12),
]
print(subdict(d, ['a', 'c']))
>>> In [5]: [{'a': 1, 'c': 3}, {'a': 2, 'c': 6}, {'a': 4, 'c': 12}]
interesting_keys = ('l', 'm', 'n')
subdict = {x: bigdict[x] for x in interesting_keys if x in bigdict}
还有一个问题(我更喜欢Mark Longair的答案)
di = {'a':1,'b':2,'c':3}
req = ['a','c','w']
dict([i for i in di.iteritems() if i[0] in di and i[0] in req])
py3.8+中另一种避免big_dict中缺少键的None值的方法使用walrus:
small_dict = {key: val for key in ('l', 'm', 'n') if (val := big_dict.get(key))}
