Python: How to check if keys exists and retrieve value from Dictionary in descending priority

Question

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

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

(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'] 

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) 

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

Answer 1

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

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

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

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

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.

Answer 2

Use .get(), which if the key is not found, returns None.

for i in keySet:     temp = myDict.get(i)     if temp is not None:         print temp         break