1def type_check(mode):
 2    """Check the types of input arguments or the output of a function."""
 3    
 4    def decorator(*expected):
 5        """Accept the expected types."""
 6        
 7        def wrapper(func):
 8            """Perform the type checking."""
 9            
10            def validation(*args, **kwargs):
11                """Validate the types of input arguments and the return the result if possible."""
12                
13                def expected_args_message():
14                    """Generate a message listing the expected argument types."""
15                    return "expected " + ", ".join([str(valid) for valid in expected]) + "!"
16                
17                if mode == 'in': 
18                    
19                    all_args = list(args) + list(kwargs.values())
20                    
21                    # Check if non-valid type is found 
22                    for arg in all_args:
23                        if not isinstance(arg, expected):
24                            print("Invalid input arguments, " + expected_args_message())
25                            return func(*args, **kwargs)
26
27                res = func(*args, **kwargs)
28                
29                # Check if return of function is non-valid type
30                if mode == 'out' and not isinstance(res, expected):
31                        print("Invalid output value, " + expected_args_message())
32    
33                return res  
34            return validation                                           
35        return wrapper
36    return decorator