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
递归解。它不是最有效的,但我发现它比其他示例更具可读性,而且它不依赖于functools。
def deep_get(d, keys):
if not keys or d is None:
return d
return deep_get(d.get(keys[0]), keys[1:])
例子
d = {'meta': {'status': 'OK', 'status_code': 200}}
deep_get(d, ['meta', 'status_code']) # => 200
deep_get(d, ['garbage', 'status_code']) # => None
一个更精致的版本
def deep_get(d, keys, default=None):
"""
Example:
d = {'meta': {'status': 'OK', 'status_code': 200}}
deep_get(d, ['meta', 'status_code']) # => 200
deep_get(d, ['garbage', 'status_code']) # => None
deep_get(d, ['meta', 'garbage'], default='-') # => '-'
"""
assert type(keys) is list
if d is None:
return default
if not keys:
return d
return deep_get(d.get(keys[0]), keys[1:], default)
其他回答
根据Yoav的回答,一个更安全的方法是:
def deep_get(dictionary, *keys):
return reduce(lambda d, key: d.get(key, None) if isinstance(d, dict) else None, keys, dictionary)
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')
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
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
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