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
在深入获取属性后,我使用点表示法安全地获得嵌套的dict值。这适用于我,因为我的字典是反序列化的MongoDB对象,所以我知道键名不包含.s。此外,在我的上下文中,我可以指定一个数据中没有的虚假回退值(None),因此在调用函数时可以避免使用try/except模式。
from functools import reduce # Python 3
def deepgetitem(obj, item, fallback=None):
"""Steps through an item chain to get the ultimate value.
If ultimate value or path to value does not exist, does not raise
an exception and instead returns `fallback`.
>>> d = {'snl_final': {'about': {'_icsd': {'icsd_id': 1}}}}
>>> deepgetitem(d, 'snl_final.about._icsd.icsd_id')
1
>>> deepgetitem(d, 'snl_final.about._sandbox.sbx_id')
>>>
"""
def getitem(obj, name):
try:
return obj[name]
except (KeyError, TypeError):
return fallback
return reduce(getitem, item.split('.'), obj)
其他回答
你可以使用get两次:
example_dict.get('key1', {}).get('key2')
如果key1或key2不存在,则返回None。
注意,如果example_dict['key1']存在但不是dict(或具有get方法的类dict对象),仍然可能引发AttributeError。如果example_dict['key1']不可下标,你发布的try..except代码将引发TypeError。
另一个区别是try…除非在第一次丢失钥匙后立即发生短路。get调用链则不然。
如果您希望保留语法example_dict['key1']['key2'],但不希望它引发KeyErrors,那么您可以使用哈希recipe:
class Hasher(dict):
# https://stackoverflow.com/a/3405143/190597
def __missing__(self, key):
value = self[key] = type(self)()
return value
example_dict = Hasher()
print(example_dict['key1'])
# {}
print(example_dict['key1']['key2'])
# {}
print(type(example_dict['key1']['key2']))
# <class '__main__.Hasher'>
注意,当缺少一个键时,返回一个空的hash。
因为Hasher是dict的一个子类,你可以像使用dict一样使用Hasher。所有相同的方法和语法都是可用的,哈希器只是以不同的方式对待缺失的键。
你可以像这样把一个普通字典转换成哈希:
hasher = Hasher(example_dict)
并将哈希转换为普通字典一样容易:
regular_dict = dict(hasher)
另一种选择是在helper函数中隐藏丑陋的代码:
def safeget(dct, *keys):
for key in keys:
try:
dct = dct[key]
except KeyError:
return None
return dct
这样你剩下的代码就可以保持相对的可读性:
safeget(example_dict, 'key1', 'key2')
我的实现下降到子字典,忽略None值,但失败与TypeError如果发现任何其他
def deep_get(d: dict, *keys, default=None):
""" Safely get a nested value from a dict
Example:
config = {'device': None}
deep_get(config, 'device', 'settings', 'light')
# -> None
Example:
config = {'device': True}
deep_get(config, 'device', 'settings', 'light')
# -> TypeError
Example:
config = {'device': {'settings': {'light': 'bright'}}}
deep_get(config, 'device', 'settings', 'light')
# -> 'light'
Note that it returns `default` is a key is missing or when it's None.
It will raise a TypeError if a value is anything else but a dict or None.
Args:
d: The dict to descend into
keys: A sequence of keys to follow
default: Custom default value
"""
# Descend while we can
try:
for k in keys:
d = d[k]
# If at any step a key is missing, return default
except KeyError:
return default
# If at any step the value is not a dict...
except TypeError:
# ... if it's a None, return default. Assume it would be a dict.
if d is None:
return default
# ... if it's something else, raise
else:
raise
# If the value was found, return it
else:
return d
递归法(мб п п и и одитс)
示例dict类型:
foo = [{'feature_name': 'Sample Creator > Contract Details > Elements of the page',
'scenarios': [{'scenario_name': 'SC, CD, Elements of the page',
'scenario_status': 'failed',
'scenario_tags': None,
'steps': [{'duration': 0,
'name': 'I open application Stage and login by '
'SPT_LOGIN and password SPT_PWD',
'status': 'untested'},
{'duration': 0,
'name': 'I open Sample Creator query page',
'status': 'untested'},
{'duration': 7.78166389465332,
'name': 'I open application Stage and login by '
'SPT_LOGIN and password SPT_PWD',
'status': 'passed'},
{'duration': 3.985326051712036,
'name': 'I open Sample Creator query page',
'status': 'passed'},
{'duration': 2.9063704013824463,
'name': 'Enter value: '
'X-2008-CON-007,X-2011-CON-016 in '
'textarea: project_text_area sleep: 1',
'status': 'passed'},
{'duration': 4.4447715282440186,
'name': 'I press on GET DATA',
'status': 'passed'},
{'duration': 1.1209557056427002,
'name': 'Verify the top table on Contract Details',
'status': 'passed'},
{'duration': 3.8173601627349854,
'name': 'I export contract_details table by offset '
'x:100, y:150',
'status': 'passed'},
{'duration': 1.032956600189209,
'name': 'Check data of '
'sc__cd_elements_of_the_page_1 and skip '
'cols None',
'status': 'passed'},
{'duration': 0.04593634605407715,
'name': "Verify 'Number of Substances' column "
'values',
'status': 'passed'},
{'duration': 0.10199904441833496,
'name': 'Substance Sample Details bottom table '
'columns',
'status': 'passed'},
{'duration': 0.0009999275207519531,
'name': 'Verify the Substance Sample Details '
'bottom table',
'status': 'passed'},
{'duration': 3.8558616638183594,
'name': 'I export substance_sample_details table '
'by offset x:100, y:150',
'status': 'passed'},
{'duration': 1.0329277515411377,
'name': 'Check data of '
'sc__cd_elements_of_the_page_2 and skip '
'cols None',
'status': 'passed'},
{'duration': 0.2879970073699951,
'name': 'Click on AG-13369',
'status': 'passed'},
{'duration': 3.800830364227295,
'name': 'I export substance_sample_details table '
'by offset x:100, y:150',
'status': 'passed'},
{'duration': 1.0169551372528076,
'name': 'Check data of '
'sc__cd_elements_of_the_page_3 and skip '
'cols None',
'status': 'passed'},
{'duration': 1.7484464645385742,
'name': 'Select all cells, table: 2',
'status': 'passed'},
{'duration': 3.812828779220581,
'name': 'I export substance_sample_details table '
'by offset x:100, y:150',
'status': 'passed'},
{'duration': 1.0029594898223877,
'name': 'Check data of '
'sc__cd_elements_of_the_page_2 and skip '
'cols None',
'status': 'passed'},
{'duration': 1.6729373931884766,
'name': 'Set window size x:800, y:600',
'status': 'passed'},
{'duration': 30.145705699920654,
'name': 'All scrollers are placed on top 6 and far '
'left 8',
'status': 'failed'}]}]},
{'feature_name': 'Sample Creator > Substance Sample History > Elements of the '
'page',
'scenarios': [{'scenario_name': 'SC, SSH, Elements of the page',
'scenario_status': 'passed',
'scenario_tags': None,
'steps': [{'duration': 0,
'name': 'I open application Stage and login by '
'SPT_LOGIN and password SPT_PWD',
'status': 'untested'},
{'duration': 0,
'name': 'I open Sample Creator query page',
'status': 'untested'},
{'duration': 7.305850505828857,
'name': 'I open application Stage and login by '
'SPT_LOGIN and password SPT_PWD',
'status': 'passed'},
{'duration': 3.500955104827881,
'name': 'I open Sample Creator query page',
'status': 'passed'},
{'duration': 3.0419492721557617,
'name': 'Enter value: NOA401800 SYN-NOA '
'A,S4A482070C SYN-ISN-OLD '
'O,S04A482167T,S04A482190Y,CSAA796564,CSCD106701 '
'in textarea: id_text_area sleep: 1',
'status': 'passed'},
{'duration': 49.567158460617065,
'name': 'I press on GET DATA',
'status': 'passed'},
{'duration': 0.13904356956481934,
'name': 'Open substance_sample_history',
'status': 'passed'},
{'duration': 1.1039845943450928,
'name': 'Columns displayed',
'status': 'passed'},
{'duration': 3.881945848464966,
'name': 'I export export_parent_table table by '
'offset x:100, y:150',
'status': 'passed'},
{'duration': 1.0334820747375488,
'name': 'Check data of '
'sc__ssh_elements_of_the_page_1 and skip '
'cols None',
'status': 'passed'},
{'duration': 0.0319981575012207,
'name': "Title is 'Additional Details for Marked "
"Rows'",
'status': 'passed'},
{'duration': 0.08897256851196289,
'name': 'Columns displayed (the same as in top '
'table)',
'status': 'passed'},
{'duration': 25.192569971084595,
'name': 'Verify the content of the bottom table',
'status': 'passed'},
{'duration': 4.308935880661011,
'name': 'I export '
'additional_details_for_marked_rows table '
'by offset x:100, y:150',
'status': 'passed'},
{'duration': 1.0089836120605469,
'name': 'Check data of '
'sc__ssh_elements_of_the_page_1 and skip '
'cols None',
'status': 'passed'}]}]}]
代码:
def get_keys(_dict: dict, prefix: list):
prefix += list(_dict.keys())
return prefix
def _loop_elements(elems:list, prefix=None, limit=None):
prefix = prefix or []
limit = limit or 9
try:
if len(elems) != 0 and isinstance(elems, list):
for _ in elems:
if isinstance(_, dict):
get_keys(_, prefix)
for item in _.values():
_loop_elements(item, prefix, limit)
return prefix[:limit]
except TypeError:
return
>>>goo = _loop_elements(foo,limit=9)
>>>goo
['feature_name', 'scenarios', 'scenario_name', 'scenario_status', 'scenario_tags', 'steps', 'duration', 'name', 'status']
对于嵌套的字典/JSON查找,可以使用dictor
PIP安装指示器
dict对象
{
"characters": {
"Lonestar": {
"id": 55923,
"role": "renegade",
"items": [
"space winnebago",
"leather jacket"
]
},
"Barfolomew": {
"id": 55924,
"role": "mawg",
"items": [
"peanut butter jar",
"waggy tail"
]
},
"Dark Helmet": {
"id": 99999,
"role": "Good is dumb",
"items": [
"Shwartz",
"helmet"
]
},
"Skroob": {
"id": 12345,
"role": "Spaceballs CEO",
"items": [
"luggage"
]
}
}
}
要获得龙星的物品,只需提供一个点分隔的路径,即
import json
from dictor import dictor
with open('test.json') as data:
data = json.load(data)
print dictor(data, 'characters.Lonestar.items')
>> [u'space winnebago', u'leather jacket']
如果键不在路径中,您可以提供回退值
你还有很多选择,比如忽略字母大小写,使用'以外的其他字符。作为路径分隔符,
https://github.com/perfecto25/dictor
你也可以使用python reduce:
def deep_get(dictionary, *keys):
return reduce(lambda d, key: d.get(key) if d else None, keys, dictionary)