Python:如何检查键是否存在以及如何从字典中检索优先级降序的值 [英] Python: How to check if keys exists and retrieve value from Dictionary in descending priority

问题描述

我有一个字典，我想根据一些键从字典中获取一些值.例如，我为用户提供了一个词典，其中包含他们的名字，姓氏，用户名，地址，年龄等.假设，我只想获取一个值(名称)-姓氏，名字或用户名，但优先级降级，如下所示:

I have a dictionary and I would like to get some values from it based on some keys. For example, I have a dictionary for users with their first name, last name, username, address, age and so on. Let's say, I only want to get one value (name) - either last name or first name or username but in descending priority like shown below:

(1)姓:如果密钥存在，则获取值并停止检查.如果不是，请移至下一个键.

(1) last name: if key exists, get value and stop checking. If not, move to next key.

(2)名:如果键存在，则获取值并停止检查.如果不是，请移至下一个键.

(2) first name: if key exists, get value and stop checking. If not, move to next key.

(3)用户名:如果键存在，则获取值或返回null/empty

(3) username: if key exists, get value or return null/empty

#my dict looks something like this
myDict = {'age': ['value'], 'address': ['value1, value2'],
          'firstName': ['value'], 'lastName': ['']}

#List of keys I want to check in descending priority: lastName > firstName > userName
keySet = ['lastName', 'firstName', 'userName']

我尝试做的是获取所有可能的值并将它们放入列表中，以便我可以检索列表中的第一个元素.显然它没有解决问题.

What I tried doing is to get all the possible values and put them into a list so I can retrieve the first element in the list. Obviously it didn't work out.

tempList = []

for key in keys:
    get_value = myDict.get(key)
    tempList .append(get_value)

有没有不使用if else块的更好的方法吗?

Is there a better way to do this without using if else block?

推荐答案

如果键的数量较少，则可以选择使用链式获取:

One option if the number of keys is small is to use chained gets:

value = myDict.get('lastName', myDict.get('firstName', myDict.get('userName')))

但是，如果您定义了keySet，这可能会更清楚:

But if you have keySet defined, this might be clearer:

value = None
for key in keySet:
    if key in myDict:
        value = myDict[key]
        break

链接的get不会短路，因此将检查所有按键，但仅会使用其中一个.如果有足够重要的键，请使用for循环.

The chained gets do not short-circuit, so all keys will be checked but only one used. If you have enough possible keys that that matters, use the for loop.

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