inclusion

Usually the field 'kind' should be allowed blank. but if it is not blank, the value should included in ['a', 'b'] validates_inclusion_of :kind, :in => ['a', 'b'], :allow_nil => true The code does not work? This syntax will perform inclusion validation while allowing nils: validates :kind, :inclusion => { :in => ['a', 'b'] }, :allow_nil => true In Rails 5 you can use allow_blank: true outside or inside inclusion block: validates :kind, inclusion: { in: ['a', 'b'], allow_blank: true } or validates :kind, inclusion: { in: ['a', 'b'] }, allow_blank: true tip: you can use in: %w(a b) for text

How to test if a python Counter is contained in another one using the following definition: A Counter a is contained in a Counter b if, and only if, for every key k in a , the value a[k] is less or equal to the value b[k] . The Counter({'a': 1, 'b': 1}) is contained in Counter({'a': 2, 'b': 2}) but it is not contained in Counter({'a': 2, 'c': 2}) . I think it is a poor design choice but in python 2.x the comparison operators ( < , <= , >= , > ) do not use the previous definition, so the third Counter is considered greater-than the first. In python 3.x , instead, Counter is an unorderable type

I found, that there is related question, about how to find if at least one item exists in a list: How to check if one of the following items is in a list? But what is the best and pythonic way to find whether all items exists in a list? Searching through the docs I found this solution: >>> l = ['a', 'b', 'c'] >>> set(['a', 'b']) <= set(l) True >>> set(['a', 'x']) <= set(l) False Other solution would be this: >>> l = ['a', 'b', 'c'] >>> all(x in l for x in ['a', 'b']) True >>> all(x in l for x in ['a', 'x']) False But here you must do more typing. Is there any other solutions? Operators like <=