Short circuit list of functions python

Question

I have a class with some method like this

class Validator:
    def _is_valid_code(self):
        return bool(#some logic here)

    def _is_valid_role(self):
        return bool(#some logic here)

    def _is_valid_age(self):
        return bool(#some logic here)
    .
    .
    .

if all of them are True I want to continue, else return a string

if not _is_valid_code():
    #short circuit and return a string
    return "not valid code"
if not _is_valid_role():
    #short circuit and return a string
    return "not valid role"
if not _is_valid_age():
    #short circuit and return a string with description
    return "not valid age"
#if we got here the request is valid so return a valid response
return valid_scenario

Now I do not have any problem with this because there are just three conditions, but for example, if I have more, let say like 10 conditions, I would end up with a lot of if scenarios, so I was thinking if something like this is possible, where I just add the condition logic and the condition to the list and that's it, the problem is to get the string value if the condition is false

conditions = [_is_valid_code(), _is_valid_role(), _is_valid_age()]
if all_conditions_true(conditions):
    return valid_scenario
else:
    return last_message_before_shortcut

Also want to know if this is valid and if this could be considered pythonic and recommended

Answer 1

You can use a dict to store the functions mapped to their respective strings.

checks = {
    _is_valid_code: "not valid code",
    _is_valid_role: "not valid role",
    _is_valid_age: "not valid age",
    }

for f in checks:
    if not f():
        return checks[f]
return valid_scenario

Note that dicts preserve insertion order in Python 3.7+. If you're using an older version or want to be stricter about the ordering, use an OrderedDict or list of tuples containing functions and strings.

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This by itself is perfectly Pythonic, but I don't know the context so I can't say for sure in your case. For example, if valid_scenario isn't a string, I'd strongly recommend using exceptions instead of having a mixed return type. This question covers that: Why should functions always return the same type? And I'd recommend the same if the functions are checking for error conditions.