python styling ** question

Question

I'm working on my first project using Python 2.7. We're coming from a Java background and our first instinct was to write python code in a Java-esque way. But now we're trying to adapt as much as possible. So far we are using pylint to adapt our code.

Now I keep running into a situation with pylint. Every time I use something like **data to pass values to a method I'm getting a pylint warning about using * or **. Now my question is: Is using ** a bad styling for writing python code? Is there some kind of standard replacement for using this ?

Regards, Bogdan

Answer 1

** can introduce some more tricky bug because it will accept anything. Usually you want code that breaks when called wrong. Here is a example:

def dostuff(**kwargs):
 force = 3
 if kwargs.get('reallyhard', False):
     force += 5 
 # and so on

# Now you need luck to find this bug  ...
dostuff(fancy=True, funky=False, realyhard=True)

You shouldn't use ** just because you are too lazy to type out the argument names. That is not always possible though, so there are legitimate uses too.

Answer 2

It's almost impossible to use static analysis to verify that the arguments generated by ** are all valid, but if it is the only appropriate mechanism them by all means do use it.