def eval_conditions(conditions=None, data={}):
'''
Evaluates conditions and returns Boolean value.
Args:
conditions (tuple) for the format of the tuple, see below
data (dict) the keys of which can be used in conditions
Returns:
(boolea)
Raises:
ValueError if an invalid operator value is specified
TypeError if:
conditions are not a 3-item tuple
the arguments of the condition don't have the same type
e.g. ('abc', 'eq', 3)
if a boolean operator does not get boolean arguments
e.g. (True, 'and', 15)
The format of the condition tuple is:
(arg1, op, arg2)
where:
arg1, arg2 can be numerical values, strings or condition tuples
op is a valid operator from the operator module
If arg is a string, and the string is a key in <data> it is treated as
a variable with value data[arg].
Notes:
* If no conditions are specified True is returned.
* empty or 0 values do *not* evaluate to booleans
'''
#CONSIDER: implementing addition/subtraction/multiplication/division
if not conditions:
return True
if isinstance(conditions, str) or isinstance(conditions, unicode):
conditions = str2tuple(conditions)
if not isinstance(conditions, tuple) or not len(conditions) == 3:
raise TypeError('conditions must be a tuple with 3 items.')
arg1 = conditions[0]
op = conditions[1]
arg2 = conditions[2]
if arg1 in data:
arg1 = data[arg1]
elif isinstance(arg1, tuple):
arg1 = eval_conditions(arg1, data)
if arg2 in data:
arg2 = data[arg2]
elif isinstance(arg2, tuple):
arg2 = eval_conditions(arg2, data)
if op in ('lt', 'le', 'eq', 'ne', 'ge', 'gt'):
if not (type(arg1) in (float, int) and type(arg2) in (float,int)) and \
type(arg1) != type(arg2):
raise TypeError('both arguments must have the same type {}, {}'.\
format(arg1, arg2))
elif op in ('and', 'or'):
if not isinstance(arg1, bool) or not isinstance(arg2, bool):
raise TypeError('boolean operator {} needs boolean arguments {},'\
' {}'.format(op, arg1, arg2))
op += '_'
else:
raise ValueError('operator {} not supported', op)
return getattr(operator, op)(arg1, arg2)
def test_str2tuple(self):
self.assertEqual(su.str2tuple("('a', 4, [1,2,3])"), ('a', 4, [1,2,3]))
self.assertIsNone(su.str2tuple("['a', 4, {1.4,}]"))
self.assertIsNone(su.str2tuple('raise SystemExit'))
self.assertIsNone(su.str2tuple('(1)'))
