Is there efficient way to validate many variables with appropriate notice?

Question

This is my code:

if self.a == "":
    raise MyException("The required parameter 'a' is empty")
if self.b == "":
    raise MyException("The required parameter 'b' is empty")
if self.v == "":
    raise MyException("The required parameter 'v' is empty")
if self.g == "":
    raise MyException("The required parameter 'g' is empty")
if self.quality == "":
    raise MyException("The required parameter 'quality' is empty")
if self.abc == "":
    raise MyException("The required parameter 'abc' is empty")

It's seems like too much repeated pattern. The issue is that I can't find a way to make it simpler and compact.

Any ideas?

Lazy solution: don't bother doing any checking at all. If your program crashes later because one of the parameters has a bad value, then mission accomplished -- the program halted and the user knows what the problem is. — Kevin, Feb 26 '19 at 13:45
@StephenRauch How would I create the name of the parameter that is missing? — Luis, Feb 26 '19 at 13:50
@Kevin My users aren't programmers. The error appear to the UI must be well written so they will know which setting is missing. I can't show them trace of error. — Luis, Feb 26 '19 at 13:50

Phydeaux · Accepted Answer · 2019-02-26T13:58:07.433

6

Assuming you still want to validate all arguments, here is a solution using getattr as suggested above:

for attribute in ["a", "b", ...]:
    if getattr(self, attribute) == "":
        raise MyException(f"The required parameter '{attribute}' is empty")

edited Feb 26 '19 at 13:58

answered Feb 26 '19 at 13:56

Phydeaux

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The problem is that I don't have ["a", "b", ...] I have [self.a, self.b] - self shouldn't be shown in the message – Luis Feb 26 '19 at 13:57
4

@Luis `getattr(self, "attribute")` is equivalent to `self.attribute` – Phydeaux Feb 26 '19 at 13:58
@Luis the message shown will be identical to the ones you have in your question – Phydeaux Feb 26 '19 at 14:01

score 1 · Answer 2 · answered Feb 26 '19 at 13:58

I wouldn't advocate for getting really fancy trying to eliminate all redundancy. Your code is easy to understand. Doing something clever with getattr() or whatnot to avoid repeating each variable name twice will turn a simple set of if statement into something significantly more complicated.

That said, this is one of the rare times where compacting the code is worth it:

if self.a == "":       raise MyException("The required parameter 'a' is empty")
if self.b == "":       raise MyException("The required parameter 'b' is empty")
if self.v == "":       raise MyException("The required parameter 'v' is empty")
if self.g == "":       raise MyException("The required parameter 'g' is empty")
if self.quality == "": raise MyException("The required parameter 'quality' is empty")
if self.abc == "":     raise MyException("The required parameter 'abc' is empty")

You could extract an exception raising method out of it; particularly valuable if you do this type of validation in many other places.

def requireNonEmpty(value, name):
    if value == "":
        raise MyException("The required parameter '{}' is empty".format(name))

requireNonEmpty(self.a, 'a')
requireNonEmpty(self.b, 'b')
requireNonEmpty(self.v, 'v')
requireNonEmpty(self.g, 'g')
requireNonEmpty(self.quality, 'quality')
requireNonEmpty(self.abc, 'abc')

Is there efficient way to validate many variables with appropriate notice?

2 Answers2