An example of my condition evaluation algorithm

condition_evaluation.py

# utility function
def cast_to_strings(varlist):
    """Cast all values in a list to string"""
    new_list = []
    for v in varlist:
        if type(v) in (int, long):
            new_list.append(str(v))
        else:
            new_list.append(v)
    return new_list


def evaluate_conditions(conditional, **kwargs):
    """
    Evaluate a list of conditions
    """
    eval_type = conditional.get('type', 'all')
    if eval_type not in ('all', 'any', 'none'):
        raise TypeError("eval_type must be 'all', 'any', or 'none'")
    conditions = conditional.get('conditions')
    if not conditions:
        raise TypeError('A list of conditions is required if a conditional is enabled')
    results = []
    for c in conditions:
        results.append(evaluate_condition(c))
    if eval_type == 'all':
        return all(results)
    elif eval_type == 'any':
        return any(results)
    elif eval_type == 'none':
        return not any(results)


def evaluate_condition(condition):
    """
    Evaluate a single condition, returning True or False.
    """
    operator = condition.get('operation')
    if not operator:
        raise TypeError('Operator required to evaluate a condition')
    values = condition.get('values')
    if not values:
        raise TypeError('Values must be present to evaluate a condition')
    # FIXME this is a bit janky but I'm leaving it for now
    values = cast_to_strings(values)
    val_to_check = condition.get('val_to_check')
    if not val_to_check:
        raise TypeError('Please supply a value to check for the condition')
    if operator == 'equals':
        return val_to_check in values
    elif operator == 'not':
        return val_to_check not in values
    else:
        raise TypeError("Unknown condition operator '%s'. Please use 'equals' or 'not'." % operator)


conditional_dict = {
    'type': 'all',
    'conditions': [
        {
            'val_to_check': 'foo',
            'operation': 'not',
            'values': ['bar', 'baz', 'buzz'],
        },
        {
            'val_to_check': 'the cake',
            'operation': 'equals',
            'values': ['a lie', 'too many carbs'],
        }
    ]
}
# Should return False since the second condition returns False
# all(True, False) => False
assert evaluate_conditions(conditional_dict) == False

Referenced by my blog post on Medium: https://medium.com/@rgutierrez1014/creating-a-condition-evaluation-algorithm-6bb24e9fc424

This has been simplified from the original implementation due to some proprietary bits