What is the scenario of dict.get('..', None) or None?

Admin 1
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if found the following code in some open source lib:

message.get('title', None) or None

is there any reason to do like this instead of message.get('title', None)?

python-3.x python
3 Answers

This will guarantee that any falsy value (e.g. None, '', 0, False, [], ...) in the dict will turn into None. i.e. if you had 

d = {'title': False}

then

d.get('title', None)  # False
d.get('title', None) or None  # None

Whether there is a practical use-case for this is debatable, but there definitely is a subtle difference...

Also note that you could simplify this to:

d.get('title') or None

since d.get defaults to returning None if no element is found.

user_7488580

If you get message and it is a false-y value this will change it to None.

For example 

message = {'title' : ''}

message.get('title', None)
>> ''

message.get('title', None) or None 
>> None
user_11589900

There is a reason.

For example, message.get('title', None) or None could return an empty string. The boolean value of an empty string in Python is False, so None will be returned instead.

This would also apply to any other value returned from the dict that evaluates to False. None will be returned instead.

Note: However, that code would be better written as message.get('title') or None, because dict.get returns None (the second argument) by default anyways.

user_19435710
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