Sometimes it's good to check things while working on them. This seems like a good way to do that.
You could probably put these in a module and just import them. from validators import * I'm interested if anyone can think of ways to improve this further. Each validator consists of an assertion with an error message if the assertion fails. The validator arguments can include an extra argument to check the return value. Less than the number of arguments is ok. Any unspecified arguments are not checked. Use Any to not check previous arguments in a list. (see the examples at the end) Cheers, Ron # ------------- Some Simple Validators. def Any(arg): pass def IsNumber(arg): assert type(arg) in (int, long, float), \ "%r is not a number" % arg def IsInt(arg): assert type(arg) in (int, long), \ "%r is not an Int" % arg def IsFloat(arg): assert isinstance(arg, float), \ "%r is not a flaot" % arg def IsLong(arg): assert isinstance(arg, long), \ "%r is not a long integer" % arg def IsString(arg): assert type(arg) in (str, unicode), \ "%r is not a string type" % arg def InRange(start, stop): def inrange(arg): assert start <= arg <= stop, \ "%r is not in range %r through %r" % (arg, start, stop) return inrange def InSet(list_): s = set(list_) def inset(arg): assert arg in s, \ "%r is not in %r" % (arg, s) return inset def LessThan(value): def lessthan(arg): assert arg < value, \ "%r is not less than %r." % (arg, value) return lessthan def MoreThan(value): def morethan(arg): assert arg > value, \ "%r is not more than %r." % (arg, value) return morethan def IsEven(arg): assert arg % 2 == 0, \ "%r is not even" % arg def IsOdd(arg): assert arg % 2 == 1, \ "%r is not odd" % arg def IsPositive(arg): assert arg >= 0, \ "%r is not positive" % arg def IsNegative(arg): assert arg < 0, \ "%r is not negative" % arg def IsTrue(arg): assert arg is True, \ "%r is not True" % arg def IsFalse(arg): assert arg is False, \ "%r is not False" % arg # ----------------- The validator decorator. def validate(*types): """ check arguments + return value against types given. """ def check_accepts(f): def new_f(*args, **kwds): assert len(types) <= len(args)+1, \ "Validators exceed arg count + return value." for (a, t) in zip(args, types): t(a) result = f(*args, **kwds) if len(types)>len(args): types[-1](result) return result new_f.func_name = f.func_name return new_f return check_accepts # -------------- Examples to play around with. @validate(Any, IsInt, IsEven) def add(a, b): return a + b @validate(InRange(1,6), InRange(1,6), LessThan(19)) def mul(a, b): return a * b # they stack too @validate(IsInt, IsInt) @validate(MoreThan(10),LessThan(10)) @validate(Any, IsPositive) def sub(a, b): return a - b @validate(IsString, IsString) def addstr(a, b): return a + b print add(3.0, 5) print mul(3, 6) print sub(11, 9) print addstr('Hello ', 'World') -- http://mail.python.org/mailman/listinfo/python-list