我有一本嵌套的字典。是否只有一种方法可以安全地传递价值观?
try:
example_dict['key1']['key2']
except KeyError:
pass
或者python有一个类似get()的方法用于嵌套字典?
我有一本嵌套的字典。是否只有一种方法可以安全地传递价值观?
try:
example_dict['key1']['key2']
except KeyError:
pass
或者python有一个类似get()的方法用于嵌套字典?
当前回答
我稍微改变了一下答案。我添加了检查,如果我们使用列表与数字。 所以现在我们可以用任何一种方法。deep_get(allTemp,[0],{})或deep_get(getMinimalTemp, [0, minimalTemperatureKey], 26)等
def deep_get(_dict, keys, default=None):
def _reducer(d, key):
if isinstance(d, dict):
return d.get(key, default)
if isinstance(d, list):
return d[key] if len(d) > 0 else default
return default
return reduce(_reducer, keys, _dict)
其他回答
def safeget(_dct, *_keys):
if not isinstance(_dct, dict): raise TypeError("Is not instance of dict")
def foo(dct, *keys):
if len(keys) == 0: return dct
elif not isinstance(_dct, dict): return None
else: return foo(dct.get(keys[0], None), *keys[1:])
return foo(_dct, *_keys)
assert safeget(dict()) == dict()
assert safeget(dict(), "test") == None
assert safeget(dict([["a", 1],["b", 2]]),"a", "d") == None
assert safeget(dict([["a", 1],["b", 2]]),"a") == 1
assert safeget({"a":{"b":{"c": 2}},"d":1}, "a", "b")["c"] == 2
你可以使用pydash:
import pydash as _ #NOTE require `pip install pydash`
_.get(example_dict, 'key1.key2', default='Default')
https://pydash.readthedocs.io/en/latest/api.html
下面是一个基于unutbu函数答案的解决方案:
Python命名指南 默认值作为参数 不用try,只是检查key是否在object上
def safe_get(dictionary, *keys, default=None):
for key in keys:
if key not in dictionary:
return default
dictionary = dictionary[key]
return dictionary
已经有很多很好的答案,但我已经提出了一个类似于JavaScript领域的lodash get的函数,它也支持通过索引进入列表:
def get(value, keys, default_value = None):
'''
Useful for reaching into nested JSON like data
Inspired by JavaScript lodash get and Clojure get-in etc.
'''
if value is None or keys is None:
return None
path = keys.split('.') if isinstance(keys, str) else keys
result = value
def valid_index(key):
return re.match('^([1-9][0-9]*|[0-9])$', key) and int(key) >= 0
def is_dict_like(v):
return hasattr(v, '__getitem__') and hasattr(v, '__contains__')
for key in path:
if isinstance(result, list) and valid_index(key) and int(key) < len(result):
result = result[int(key)] if int(key) < len(result) else None
elif is_dict_like(result) and key in result:
result = result[key]
else:
result = default_value
break
return result
def test_get():
assert get(None, ['foo']) == None
assert get({'foo': 1}, None) == None
assert get(None, None) == None
assert get({'foo': 1}, []) == {'foo': 1}
assert get({'foo': 1}, ['foo']) == 1
assert get({'foo': 1}, ['bar']) == None
assert get({'foo': 1}, ['bar'], 'the default') == 'the default'
assert get({'foo': {'bar': 'hello'}}, ['foo', 'bar']) == 'hello'
assert get({'foo': {'bar': 'hello'}}, 'foo.bar') == 'hello'
assert get({'foo': [{'bar': 'hello'}]}, 'foo.0.bar') == 'hello'
assert get({'foo': [{'bar': 'hello'}]}, 'foo.1') == None
assert get({'foo': [{'bar': 'hello'}]}, 'foo.1.bar') == None
assert get(['foo', 'bar'], '1') == 'bar'
assert get(['foo', 'bar'], '2') == None
一个简单的类,可以包装字典,并根据键进行检索:
class FindKey(dict):
def get(self, path, default=None):
keys = path.split(".")
val = None
for key in keys:
if val:
if isinstance(val, list):
val = [v.get(key, default) if v else None for v in val]
else:
val = val.get(key, default)
else:
val = dict.get(self, key, default)
if not val:
break
return val
例如:
person = {'person':{'name':{'first':'John'}}}
FindDict(person).get('person.name.first') # == 'John'
如果该键不存在,则默认返回None。你可以在FindDict包装器中使用default=键覆盖它,例如':
FindDict(person, default='').get('person.name.last') # == doesn't exist, so ''