def require(*types):
'''
Return a decorator function that requires specified types.
types -- tuple each element of which is a type or class or a tuple of
several types or classes.
Example to require a string then a numeric argument
@require(str, (int, long, float))
will do the trick
'''
def deco(func):
'''
Decorator function to be returned from require(). Returns a function
wrapper that validates argument types.
'''
def wrapper (*args):
'''
Function wrapper that checks argument types.
'''
assert len(args) == len(types), 'Wrong number of arguments.'
for a, t in zip(args, types):
if type(t) == type(()):
# any of these types are ok
assert sum(isinstance(a, tp) for tp in t) > 0, '''\
%s is not a valid type. Valid types:
%s
''' % (a, '\n'.join(str(x) for x in t))
assert isinstance(a, t), '%s is not a %s type' % (a, t)
return func(*args)
return wrapper
return deco
@require(int)
def inter(int_val):
print 'int_val is ', int_val
@require(float)
def floater(f_val):
print 'f_val is ', f_val
@require(str, (int, long, float))
def nameAge1(name, age):
print '%s is %s years old' % (name, age)
# another way to do the same thing
number = (int, float, long)
@require(str, number)
def nameAge2(name, age):
print '%s is %s years old' % (name, age)
nameAge1('Emily', 8) # str, int ok
nameAge1('Elizabeth', 4.5) # str, float ok
nameAge2('Romita', 9L) # str, long ok
nameAge2('Emily', 'eight') # raises an exception!
