1 import sys
   2 
   3 def propget(func):
   4     locals = sys._getframe(1).f_locals
   5     name = func.__name__
   6     prop = locals.get(name)
   7     if not isinstance(prop, property):
   8         prop = property(func, doc=func.__doc__)
   9     else:
  10         doc = prop.__doc__ or func.__doc__
  11         prop = property(func, prop.fset, prop.fdel, doc)
  12     return prop
  13 
  14 def propset(func):
  15     locals = sys._getframe(1).f_locals
  16     name = func.__name__
  17     prop = locals.get(name)
  18     if not isinstance(prop, property):
  19         prop = property(None, func, doc=func.__doc__)
  20     else:
  21         doc = prop.__doc__ or func.__doc__
  22         prop = property(prop.fget, func, prop.fdel, doc)
  23     return prop
  24 
  25 def propdel(func):
  26     locals = sys._getframe(1).f_locals
  27     name = func.__name__
  28     prop = locals.get(name)
  29     if not isinstance(prop, property):
  30         prop = property(None, None, func, doc=func.__doc__)
  31     else:
  32         prop = property(prop.fget, prop.fset, func, prop.__doc__)
  33     return prop
  34 
  35 # These can be used like this:
  36 
  37 class Example(object):
  38 
  39     @propget
  40     def myattr(self):
  41         return self._half * 2
  42 
  43     @propset
  44     def myattr(self, value):
  45         self._half = value / 2
  46 
  47     @propdel
  48     def myattr(self):
  49         del self._half

   1 class Example(object):
   2     @apply
   3     def myattr():
   4         doc = """This is the doc string."""
   5 
   6         def fget(self):
   7             return self._half * 2
   8 
   9         def fset(self, value):
  10             self._half = value / 2
  11 
  12         def fdel(self):
  13             del self._half
  14 
  15         return property(**locals())

   1 def Property(function):
   2     keys = 'fget', 'fset', 'fdel'
   3     func_locals = {'doc':function.__doc__}
   4     def probeFunc(frame, event, arg):
   5         if event == 'return':
   6             locals = frame.f_locals
   7             func_locals.update(dict((k,locals.get(k)) for k in keys))
   8             sys.settrace(None)
   9         return probeFunc
  10     sys.settrace(probeFunc)
  11     function()
  12     return property(**func_locals)
  13 
  14 #====== Example =======================================================
  15 
  16 from math import radians, degrees, pi
  17 
  18 class Angle(object):
  19     def __init__(self,rad):
  20         self._rad = rad
  21 
  22     @Property
  23     def rad():
  24         '''The angle in radians'''
  25         def fget(self):
  26             return self._rad
  27         def fset(self,angle):
  28             if isinstance(angle,Angle): angle = angle.rad
  29             self._rad = float(angle)
  30 
  31     @Property
  32     def deg():
  33         '''The angle in degrees'''
  34         def fget(self):
  35             return degrees(self._rad)
  36         def fset(self,angle):
  37             if isinstance(angle,Angle): angle = angle.deg
  38             self._rad = radians(angle)

   1 class memoized(object):
   2    """Decorator that caches a function's return value each time it is called.
   3    If called later with the same arguments, the cached value is returned, and
   4    not re-evaluated.
   5    """
   6    def __init__(self, func):
   7       self.func = func
   8       self.cache = {}
   9    def __call__(self, *args):
  10       try:
  11          return self.cache[args]
  12       except KeyError:
  13          self.cache[args] = value = self.func(*args)
  14          return value
  15       except TypeError:
  16          # uncachable -- for instance, passing a list as an argument.
  17          # Better to not cache than to blow up entirely.
  18          return self.func(*args)
  19    def __repr__(self):
  20       """Return the function's docstring."""
  21       return self.func.__doc__
  22 
  23 @memoized
  24 def fibonacci(n):
  25    "Return the nth fibonacci number."
  26    if n in (0, 1):
  27       return n
  28    return fibonacci(n-1) + fibonacci(n-2)
  29 
  30 print fibonacci(12)

   1 class curried(object):
   2   """
   3   Decorator that returns a function that keeps returning functions
   4   until all arguments are supplied; then the original function is
   5   evaluated.
   6   """
   7 
   8   def __init__(self, func, *a):
   9     self.func = func
  10     self.args = a
  11   def __call__(self, *a):
  12     args = self.args + a
  13     if len(args) < self.func.func_code.co_argcount:
  14       return curried(self.func, *args)
  15     else:
  16       return self.func(*args)
  17 
  18 
  19 @curried
  20 def add(a, b):
  21     return a+b
  22 
  23 add1 = add(1)
  24 
  25 print add1(2)

   1 import sys
   2 
   3 WHAT_TO_DEBUG = set(['io', 'core'])  # change to what you need
   4 
   5 class debug:
   6     """ Decorator which helps to control what aspects of a program to debug
   7     on per-function basis. Aspects are provided as list of arguments.
   8     It DOESN'T slowdown functions which aren't supposed to be debugged.
   9     """
  10     def __init__(self, aspects=None):
  11         self.aspects = set(aspects)
  12 
  13     def __call__(self, f):
  14         if self.aspects & WHAT_TO_DEBUG:
  15             def newf(*args, **kwds):
  16                 print >> sys.stderr, f.func_name, args, kwds
  17                 f_result = f(*args, **kwds)
  18                 print >> sys.stderr, f.func_name, "returned", f_result
  19                 return f_result
  20             newf.__doc__ = f.__doc__
  21             return newf
  22         else:
  23             return f
  24 
  25 @debug(['io'])
  26 def prn(x):
  27     print x
  28 
  29 @debug(['core'])
  30 def mult(x, y):
  31     return x * y
  32 
  33 prn(mult(2,2))

   1 class Foo:
   2     def __init__(self):
   3         self.x = 42
   4 
   5 foo = Foo()
   6 
   7 def addto(instance):
   8     def decorator(f):
   9         import new
  10         f = new.instancemethod(f, instance, instance.__class__)
  11         setattr(instance, f.func_name, f)
  12         return f
  13     return decorator
  14 
  15 @addto(foo)
  16 def print_x(self):
  17     print self.x
  18 
  19 # foo.print_x() would print "42"

   1 class countcalls(object):
   2    "Decorator that keeps track of the number of times a function is called."
   3 
   4    __instances = {}
   5 
   6    def __init__(self, f):
   7       self.__f = f
   8       self.__numCalls = 0
   9       countcalls.__instances[f] = self
  10 
  11    def __call__(self, *args, **kwargs):
  12       self.__numCalls += 1
  13       return self.__f(*args, **kwargs)
  14 
  15    @staticmethod
  16    def count(f):
  17       "Return the number of times the function f was called."
  18       return countcalls.__instances[f].__numCalls
  19 
  20    @staticmethod
  21    def counts():
  22       "Return a dict of {function: # of calls} for all registered functions."
  23       return dict([(f, countcalls.count(f)) for f in countcalls.__instances])

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

   1 def simple_decorator(decorator):
   2     """This decorator can be used to turn simple functions
   3     into well-behaved decorators, so long as the decorators
   4     are fairly simple. If a decorator expects a function and
   5     returns a function (no descriptors), and if it doesn't
   6     modify function attributes or docstring, then it is
   7     eligible to use this. Simply apply @simple_decorator to
   8     your decorator and it will automatically preserve the
   9     docstring and function attributes of functions to which
  10     it is applied."""
  11     def new_decorator(f):
  12         g = decorator(f)
  13         g.__name__ = f.__name__
  14         g.__doc__ = f.__doc__
  15         g.__dict__.update(f.__dict__)
  16         return g
  17     # Now a few lines needed to make simple_decorator itself
  18     # be a well-behaved decorator.
  19     new_decorator.__name__ = decorator.__name__
  20     new_decorator.__doc__ = decorator.__doc__
  21     new_decorator.__dict__.update(decorator.__dict__)
  22     return new_decorator
  23 
  24 #
  25 # Sample Use:
  26 #
  27 @simple_decorator
  28 def mySimpleLoggingDecorator( func ):
  29     def logged_func( *args, **kwargs ):
  30         print 'calling %s' % func.__name__
  31         return func( *args, **kwargs )
  32     return logged_func
  33 
  34 @mySimpleLoggingDecorator
  35 def double(x):
  36     "Doubles a number"
  37     return 2*x
  38 
  39 assert double.__name__ == 'double'
  40 assert double.__doc__ == 'Doubles a number'
  41 print double(155)

   1 def unchanged(func):
   2     "This decorator doesn't add any behavior"
   3     return func
   4 
   5 def disabled(func):
   6     "This decorator disables the provided function, and does nothing"
   7     def emptyFunc(*args,**kargs):
   8         pass
   9     return emptyFunc
  10 
  11 # define this as equivalent to unchanged, for nice symmetry with disabled
  12 enabled = unchanged
  13 
  14 #
  15 # Sample use
  16 #
  17 
  18 globalEnableFlag = int(True)
  19 
  20 state = (disabled, enabled)[globalEnableFlag]
  21 @state
  22 def specialFunctionFoo():
  23     print "function was enabled"

   1 def dumpArgs(func):
   2     "This decorator dumps out the arguments passed to a function before calling it"
   3     argnames = func.func_code.co_varnames[:func.func_code.co_argcount]
   4     fname = func.func_name
   5     def echoFunc(*args,**kwargs):
   6         print fname, ":", ', '.join('%s=%r' % entry
   7                                     for entry in zip(argnames,args) + kwargs.items())
   8         return func(*args, **kwargs)
   9     return echoFunc
  10 
  11 @dumpArgs
  12 def f1(a,b,c):
  13     print a + b + c
  14 
  15 f1(1, 2, 3)

   1 """
   2 Provide pre-/postconditions as function decorators.
   3 
   4 Example usage:
   5 
   6   >>> def in_ge20(inval):
   7   ...    assert inval >= 20, 'Input value < 20'
   8   ...
   9   >>> def out_lt30(retval, inval):
  10   ...    assert retval < 30, 'Return value >= 30'
  11   ...
  12   >>> @precondition(in_ge20)
  13   ... @postcondition(out_lt30)
  14   ... def inc(value):
  15   ...   return value + 1
  16   ...
  17   >>> inc(5)
  18   Traceback (most recent call last):
  19     ...
  20   AssertionError: Input value < 20
  21   >>> inc(29)
  22   Traceback (most recent call last):
  23     ...
  24   AssertionError: Return value >= 30
  25   >>> inc(20)
  26   21
  27 
  28 You can define as many pre-/postconditions for a function as you
  29 like. It is also possible to specify both types of conditions at once:
  30 
  31   >>> @conditions(in_ge20, out_lt30)
  32   ... def add1(value):
  33   ...   return value + 1
  34   ...
  35   >>> add1(5)
  36   Traceback (most recent call last):
  37     ...
  38   AssertionError: Input value < 20
  39 
  40 An interesting feature is the ability to prevent the creation of
  41 pre-/postconditions at function definition time. This makes it
  42 possible to use conditions for debugging and then switch them off for
  43 distribution.
  44 
  45   >>> debug = False
  46   >>> @precondition(in_ge20, debug)
  47   ... def dec(value):
  48   ...   return value - 1
  49   ...
  50   >>> dec(5)
  51   4
  52 """
  53 
  54 __all__ = [ 'precondition', 'postcondition', 'conditions' ]
  55 
  56 DEFAULT_ON = True
  57 
  58 def precondition(precondition, use_conditions=DEFAULT_ON):
  59     return conditions(precondition, None, use_conditions)
  60 
  61 def postcondition(postcondition, use_conditions=DEFAULT_ON):
  62     return conditions(None, postcondition, use_conditions)
  63 
  64 class conditions(object):
  65     __slots__ = ('__precondition', '__postcondition')
  66 
  67     def __init__(self, pre, post, use_conditions=DEFAULT_ON):
  68         if not use_conditions:
  69             pre, post = None, None
  70 
  71         self.__precondition  = pre
  72         self.__postcondition = post
  73 
  74     def __call__(self, function):
  75         # combine recursive wrappers (@precondition + @postcondition == @conditions)
  76         pres  = set( (self.__precondition,) )
  77         posts = set( (self.__postcondition,) )
  78 
  79         # unwrap function, collect distinct pre-/post conditions
  80         while type(function) is FunctionWrapper:
  81             pres.add(function._pre)
  82             posts.add(function._post)
  83             function = function._func
  84 
  85         # filter out None conditions and build pairs of pre- and postconditions
  86         conditions = map(None, filter(None, pres), filter(None, posts))
  87 
  88         # add a wrapper for each pair (note that 'conditions' may be empty)
  89         for pre, post in conditions:
  90             function = FunctionWrapper(pre, post, function)
  91 
  92         return function
  93 
  94 class FunctionWrapper(object):
  95     def __init__(self, precondition, postcondition, function):
  96         self._pre  = precondition
  97         self._post = postcondition
  98         self._func = function
  99 
 100     def __call__(self, *args, **kwargs):
 101         precondition  = self._pre
 102         postcondition = self._post
 103 
 104         if precondition:
 105             precondition(*args, **kwargs)
 106         result = self._func(*args, **kwargs)
 107         if postcondition:
 108             postcondition(result, *args, **kwargs)
 109         return result
 110 
 111 def __test():
 112     import doctest
 113     doctest.testmod()
 114 
 115 if __name__ == "__main__":
 116     __test()

   1 import warnings
   2 def decorating(func, doc=''):
   3     def provideatts(newFunc, ):
   4         newFunc.__name__ = func.__name__
   5         newFunc.__doc__ = (func.__doc__ or '') + '\n' + doc
   6         newFunc.__dict__.update(func.__dict__)
   7         return newFunc
   8     return provideatts
   9 
  10 # Example use:
  11 def deprecated(func):
  12     @decorating(func, doc='(Deprecated.)')
  13     def you_will_never_see_this_name(*args, **kwargs):
  14         warnings.warn("Call to deprecated function %s." % func.__name__,
  15                           category=DeprecationWarning)
  16         return func(*args, **kwargs)
  17     return you_will_never_see_this_name

   1 import sys
   2 import os
   3 import linecache
   4 
   5 def trace(f):
   6     def globaltrace(frame, why, arg):
   7         if why == "call":
   8             return localtrace
   9         return None
  10 
  11     def localtrace(frame, why, arg):
  12         if why == "line":
  13             # record the file name and line number of every trace
  14             filename = frame.f_code.co_filename
  15             lineno = frame.f_lineno
  16 
  17             bname = os.path.basename(filename)
  18             print "%s(%d): %s" % (bname, lineno,
  19                                   linecache.getline(filename, lineno)),
  20         return localtrace
  21 
  22     def _f(*args, **kwds):
  23         sys.settrace(globaltrace)
  24         result = f(*args, **kwds)
  25         sys.settrace(None)
  26         return result
  27 
  28     return _f

   1 def synchronized(lock):
   2     """ Synchronization decorator. """
   3 
   4     def wrap(f):
   5         def newFunction(*args, **kw):
   6             lock.acquire()
   7             try:
   8                 return f(*args, **kw)
   9             finally:
  10                 lock.release()
  11         return newFunction
  12     return wrap
  13 
  14 # Example usage:
  15 
  16 from threading import Lock
  17 myLock = Lock()
  18 
  19 @synchronized(myLock)
  20 def critical1(*args):
  21     # Interesting stuff goes here.
  22     pass
  23 
  24 @synchronized(myLock)
  25 def critical2(*args):
  26     # Other interesting stuff goes here.
  27     pass

   1 """
   2 One of three degrees of enforcement may be specified by passing
   3 the 'debug' keyword argument to the decorator:
   4     0 -- NONE:   No type-checking. Decorators disabled.
   5     1 -- MEDIUM: Print warning message to stderr. (Default)
   6     2 -- STRONG: Raise TypeError with message.
   7 If 'debug' is not passed to the decorator, the default level is used.
   8 
   9 Example usage:
  10     >>> NONE, MEDIUM, STRONG = 0, 1, 2
  11     >>>
  12     >>> @accepts(int, int, int)
  13     ... @returns(float)
  14     ... def average(x, y, z):
  15     ...     return (x + y + z) / 2
  16     ...
  17     >>> average(5.5, 10, 15.0)
  18     TypeWarning:  'average' method accepts (int, int, int), but was given
  19     (float, int, float)
  20     15.25
  21     >>> average(5, 10, 15)
  22     TypeWarning:  'average' method returns (float), but result is (int)
  23     15
  24 
  25 Needed to cast params as floats in function def (or simply divide by 2.0).
  26 
  27     >>> TYPE_CHECK = STRONG
  28     >>> @accepts(int, debug=TYPE_CHECK)
  29     ... @returns(int, debug=TYPE_CHECK)
  30     ... def fib(n):
  31     ...     if n in (0, 1): return n
  32     ...     return fib(n-1) + fib(n-2)
  33     ...
  34     >>> fib(5.3)
  35     Traceback (most recent call last):
  36       ...
  37     TypeError: 'fib' method accepts (int), but was given (float)
  38 
  39 """
  40 import sys
  41 
  42 def accepts(*types, **kw):
  43     """ Function decorator. Checks that inputs given to decorated function
  44     are of the expected type.
  45 
  46     Parameters:
  47     types -- The expected types of the inputs to the decorated function.
  48              Must specify type for each parameter.
  49     kw    -- Optional specification of 'debug' level (this is the only valid
  50              keyword argument, no other should be given).
  51              debug=( 0 | 1 | 2 )
  52 
  53     """
  54     if not kw:
  55         # default level: MEDIUM
  56         debug = 1
  57     else:
  58         debug = kw['debug']
  59     try:
  60         def decorator(f):
  61             def newf(*args):
  62                 if debug == 0:
  63                     return f(*args)
  64                 assert len(args) == len(types)
  65                 argtypes = tuple(map(type, args))
  66                 if argtypes != types:
  67                     msg = info(f.__name__, types, argtypes, 0)
  68                     if debug == 1:
  69                         print >> sys.stderr, 'TypeWarning: ', msg
  70                     elif debug == 2:
  71                         raise TypeError, msg
  72                 return f(*args)
  73             newf.__name__ = f.__name__
  74             return newf
  75         return decorator
  76     except KeyError, key:
  77         raise KeyError, key + "is not a valid keyword argument"
  78     except TypeError, msg:
  79         raise TypeError, msg
  80 
  81 
  82 def returns(ret_type, **kw):
  83     """ Function decorator. Checks that return value of decorated function
  84     is of the expected type.
  85 
  86     Parameters:
  87     ret_type -- The expected type of the decorated function's return value.
  88                 Must specify type for each parameter.
  89     kw       -- Optional specification of 'debug' level (this is the only valid
  90                 keyword argument, no other should be given).
  91                 debug=( 0 | 1 | 2 )
  92 
  93     """
  94     try:
  95         if not kw:
  96             # default level: MEDIUM
  97             debug = 1
  98         else:
  99             debug = kw['debug']
 100         def decorator(f):
 101             def newf(*args):
 102                 result = f(*args)
 103                 if debug == 0:
 104                     return result
 105                 res_type = type(result)
 106                 if res_type != ret_type:
 107                     msg = info(f.__name__, (ret_type,), (res_type,), 1)
 108                     if debug == 1:
 109                         print >> sys.stderr, 'TypeWarning: ', msg
 110                     elif debug == 2:
 111                         raise TypeError, msg
 112                 return result
 113             newf.__name__ = f.__name__
 114             return newf
 115         return decorator
 116     except KeyError, key:
 117         raise KeyError, key + "is not a valid keyword argument"
 118     except TypeError, msg:
 119         raise TypeError, msg
 120 
 121 def info(fname, expected, actual, flag):
 122     """ Convenience function returns nicely formatted error/warning msg. """
 123     format = lambda types: ', '.join([str(t).split("'")[1] for t in types])
 124     expected, actual = format(expected), format(actual)
 125     msg = "'%s' method " % fname \
 126           + ("accepts", "returns")[flag] + " (%s), but " % expected\
 127           + ("was given", "result is")[flag] + " (%s)" % actual
 128     return msg

   1 class CGImethod(object):
   2     def __init__(self,title):
   3         self.title = title
   4     def __call__(self,fn):
   5         def wrappedFn(*args):
   6             print "Content-Type: text/html\n\n"
   7             print "<HTML>"
   8             print "<HEAD><TITLE>%s</TITLE></HEAD>" % self.title
   9             print "<BODY>"
  10             try:
  11                 fn(*args)
  12             except Exception,e:
  13                 print
  14                 print e
  15                 raise
  16             finally:
  17                 print
  18                 print "</BODY></HTML>"
  19         return wrappedFn
  20 
  21 @CGIMethod("Hello with Decorator")
  22 def sayHello():
  23     print '<h1>Hello from CGI-Land</h1>'