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
unutbu回答的一个改编,我发现在我自己的代码中很有用:
example_dict.setdefaut('key1', {}).get('key2')
如果key1还没有这个键,它会为它生成一个字典条目,以避免出现KeyError。如果您希望像我这样以包含键对的嵌套字典结束,这似乎是最简单的解决方案。
其他回答
从Python 3.4开始,你可以使用suppress (KeyError)来访问嵌套的json对象,而不用担心KeyError
from contextlib import suppress
with suppress(KeyError):
a1 = json_obj['key1']['key2']['key3']
a2 = json_obj['key4']['key5']['key6']
a3 = json_obj['key7']['key8']['key9']
Techdragon提供。看看他的回答,了解更多细节:https://stackoverflow.com/a/45874251/1189659
如果您想使用另一个库来解决问题,这是最好的方法
https://github.com/maztohir/dict-path
from dict-path import DictPath
data_dict = {
"foo1": "bar1",
"foo2": "bar2",
"foo3": {
"foo4": "bar4",
"foo5": {
"foo6": "bar6",
"foo7": "bar7",
},
}
}
data_dict_path = DictPath(data_dict)
data_dict_path.get('key1/key2/key3')
对于二级键检索,你可以这样做:
key2_value = (example_dict.get('key1') or {}).get('key2')
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
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