[ Python 文章收集 ] How Python deprecate function by decorator

Source From Here 
Introduction 
Java has the "@deprecated" flag (in javadocs) which is used to mark a method as no-longer-current and generates a warning if the method is used. Python can do the same thing. 

How-To 
Try below sample code: 
- Deprecated.py 

view plaincopy to clipboardprint?

1. #!/usr/bin/env python  
2. import warnings  
3.   
4. def deprecated(func):  
5.     """This is a decorator which can be used to mark functions  
6.     as deprecated. It will result in a warning being emmitted  
7.     when the function is used."""  
8.     def newFunc(*args, **kwargs):  
9.         warnings.warn("Call to deprecated function %s." % func.__name__,  
10.                       category=DeprecationWarning,  
11.                       stacklevel=2)  
12.         return func(*args, **kwargs)  
13.     newFunc.__name__ = func.__name__  
14.     newFunc.__doc__ = func.__doc__  
15.     newFunc.__dict__.update(func.__dict__)  
16.     return newFunc  
17.   
18.   
19.   
20. # === Examples of use ===  
21. @deprecated  
22. def some_old_function(x,y):  
23.     return x + y  
24.   
25. class SomeClass:  
26.     @deprecated  
27.     def some_old_method(self, x,y):  
28.         return x + y  
29.   
30. print("Test deprecated function: %s" % (some_old_function(1,2)))  
31. obj = SomeClass()  
32. print("Test deprecated object func: %s" % (obj.some_old_method(1,2)))  

Execution result: 

// - W arg: Warning control. Python’s warning machinery by default prints warning messages to sys.stderr.
# python -W all Deprecated.py
Deprecated.py:30: DeprecationWarning: Call to deprecated function some_old_function.
print("Test deprecated function: %s" % (some_old_function(1,2)))
Test deprecated function: 3
Deprecated.py:32: DeprecationWarning: Call to deprecated function some_old_method.
print("Test deprecated object func: %s" % (obj.some_old_method(1,2)))
Test deprecated object func: 3

Supplement 
* Python stdlib - warnings - Warning Control 

Warning messages are typically issued in situations where it is useful to alert the user of some condition in a program, where that condition (normally) doesn’t warrant raising an exception and terminating the program. For example, one might want to issue a warning when a program uses an obsolete module...

* [Python 學習筆記] 進階議題 : 修飾器 (函式修飾器)