Assigning a Django Model's field to a value if it matches a condition.

g = Car.objects.get(pk=1234)

g.data_version = my_dict['dataVersion'] if my_dict else expression_false # Do nothing??

How do I do nothing in that case? We can't do if conditional else pass.

I know I can do:

if my_dict:

g.data_version = my_dict['dataVersion']

but I was wondering if there was a way to do inline expression_true if conditional else do nothing.

解决方案

No, you can't do exactly what you are describing, as it wouldn't make sense. You are assigning to the variable g.data_version... so you must assign something. What you describe would be like writing:

g.data_version = # There is nothing else here

Which is obviously invalid syntax. And really, there's no reason to do it. You should either do:

if my_dict:

g.data_version = my_dict['dataVersion']

or

g.data_version = my_dict['dataVersion'] if my_dict else None # or 0 or '' depending on what data_version should be.

Technically, you could also do:

g.data_version = my_dict['dataVersion'] if my_dict else g.data_version

if you only want to update g.data_version if your dict exists, but this is less readable and elegant than just using a normal if statement.