Core Python Programming (2nd Edition)

Creation time, modification time, and access time are familiar attributes of files, but nothing says that
you cannot add this type of information to objects. After all, certain applications may benefit from these
additional pieces of information.
If you are unfamiliar with using these three pieces of chronological data, we will attempt to clarify them.
The creation time (or "ctime") is the time of instantiation, the modification time (or "mtime") refers to
the time that the core data was updated [accomplished by calling the new set() method], and the
access time (or "atime") is the timestamp of when the data value of the object was last retrieved or an
attribute was accessed.
Proceeding to updating the class we defined earlier, we create the module twrapme.py, given in Example
13.7.
Example 13.7. Wrapping Standard Types (twrapme.py)
Class definition that wraps any built-in type, adding time attributes; get(), set(), and string
representation methods; and delegating all remaining attribute access to those of the
standard type.
1 #!/usr/bin/env python
2
3 from time import time, ctime
4
5 class TimedWrapMe(object):
6
7 def __init__(self, obj):
8 self.__data = obj
9 self.__ctime = self.__mtime = \
10 self.__atime = time()
11
12 def get(self):
13 self.__atime = time()
14 return self.__data
15
16 def gettimeval(self, t_type):
17 if not isinstance(t_type, str) or \
18 t_type[0] not in 'cma':
19 raise TypeError, \
20 "argument of 'c', 'm', or 'a' req'd"
21 return getattr(self, '_%s__%stime' % \
22 (self.__class__.__name__, t_type[0]))
23
24 def gettimestr(self, t_type):
25 return ctime(self.gettimeval(t_type))
26
27 def set(self, obj):
28 self.__data = obj
29 self.__mtime = self.__atime = time()
30
31 def __repr__(self): # repr()
32 self.__atime = time()
33 return 'self.__data'
34
35 def __str__(self): # str()
36 self.__atime = time()
37 return str(self.__data)