Python check if isinstance any type in list?

Question

How do I pythonicly do:

var = 7.0
var_is_good = isinstance(var, classinfo1) or isinstance(var, classinfo2) or isinstance(var, classinfo3) or ... or  isinstance(v         


        

Answer 1

isinstance() takes a tuple of classes for the second argument. It'll return true if the first argument is an instance of any of the types in that sequence:

isinstance(var, (classinfo1, classinfo2, classinfo3))

In other words, isinstance() already offers this functionality, out of the box.

From the isinstance() documentation:

If classinfo is neither a class object nor a type object, it may be a tuple of class or type objects, or may recursively contain other such tuples (other sequence types are not accepted).

Emphasis mine; note the recursive nature; (classinfo1, (classinfo2, classinfo3)) is also a valid option.

Answer 2

This will solve your problem:

valid_instance_types = <tuple of types you want to allow>
var_is_good = isinstance(var, valid_instance_types)

Based on the documentation there are a lot of ways you can pass values of types in to isinstance.

You might also look into voluptuous if you're trying to do a more complicated validation of which this is just a part.

Answer 3

You were pretty close with the title of your question already. You could use any and a list:

var = 7.0
var_is_good = any([isinstance(var, classinfo1),
                   isinstance(var, classinfo2),
                   isinstance(var, classinfo3), ...
                   isinstance(var, classinfoN)])

But looking in the docs of isinstance reveals:

Return true if the object argument is an instance of the classinfo argument, or of a (direct, indirect or virtual) subclass thereof. If object is not an object of the given type, the function always returns false. If classinfo is not a class (type object), it may be a tuple of type objects, or may recursively contain other such tuples (other sequence types are not accepted). If classinfo is not a type or tuple of types and such tuples, a TypeError exception is raised.

This means the better way to do it is

var = 7.0
var_is_good = isinstance(var, (classinfo1,
                               classinfo2,
                               classinfo3,
                               ...,
                               classinfoN))

Answer 4

You generally shouldn't be using isinstance, but what you're wanting to do can be accomplished with the any() builtin function.

var_is_good = any(isinstance(var, t) for t in [type1, type2, type3])