Source Code for Module turbogears.decorator

  1  """Decorator tools""" 
  2   
  3  __all__ = ['decorate', 'make_weak_signature', 'compose', 
  4      'decorator', 'weak_signature_decorator', 
  5      'simple_decorator', 'simple_weak_signature_decorator', 
  6      'func_id', 'func_eq', 'func_original', 'func_composition'] 
  7   
  8  import itertools 
  9  from inspect import getargspec, formatargspec 
 10   
 11   
 12 -def decorate(func, caller, signature=None): 
 13      """Decorate func with caller. 
 14   
 15      Inspired by Michele Simionato's decorator library: 
 16      http://www.phyast.pitt.edu/~micheles/python/documentation.html 
 17   
 18      """ 
 19      argnames, varargs, kwargs, defaults = \ 
 20          signature is None and getargspec(func) or signature 
 21      if defaults is None: 
 22          defaults = () 
 23      parameters = formatargspec(argnames, varargs, kwargs, defaults)[1:-1] 
 24      defval = itertools.count(len(argnames) - len(defaults)) 
 25      args = formatargspec(argnames, varargs, kwargs, defaults, 
 26          formatvalue=lambda value:"=%s" % argnames[defval.next()])[1:-1] 
 27      exec_dict = dict(func=func, caller=caller) 
 28      exec "\ndef %s(%s):\n\treturn caller(func, %s)\n" % ( 
 29          func.__name__, parameters, args) in exec_dict 
 30      new_func = exec_dict[func.__name__] 
 31      new_func.__doc__ = func.__doc__ 
 32      new_func.__dict__ = func.__dict__.copy() 
 33      new_func.__module__ = func.__module__ 
 34      new_func.__composition__ = getattr(func, '__composition__', 
 35          [func]) + [new_func] 
 36      return new_func 
 37   
 38   
 39 -def decorator(entangler, signature=None): 
 40      """Decorate function with entangler. 
 41   
 42      Use new signature or preserve original signature if signature is None. 
 43   
 44      """ 
 45      def entangle(func): 
 46          return decorate(func, entangler(func), signature) 
 47      return entangle 
 48   
 49   
 50 -def weak_signature_decorator(entangler): 
 51      """Decorate function with entangler and weak signature. 
 52   
 53      Changes signature to accept arbitrary additional arguments. 
 54   
 55      """ 
 56      def entangle(func): 
 57          return decorate(func, entangler(func), make_weak_signature(func)) 
 58      return entangle 
 59   
 60   
 61 -def simple_decorator(caller, signature=None): 
 62      """Decorate function with caller.""" 
 63      def entangle(func): 
 64          return decorate(func, caller, signature) 
 65      return entangle 
 66   
 67   
 68 -def simple_weak_signature_decorator(caller): 
 69      """Decorate function with caller and weak signature. 
 70   
 71      Changes signature to accept arbitrary additional arguments. 
 72   
 73      """ 
 74      def entangle(func): 
 75          return decorate(func, caller, make_weak_signature(func)) 
 76      return entangle 
 77   
 78   
 79 -def make_weak_signature(func): 
 80      """Change signature to accept arbitrary additional arguments.""" 
 81      argnames, varargs, kwargs, defaults = getargspec(func) 
 82      if kwargs is None: 
 83          kwargs = "_decorator__kwargs" 
 84      if varargs is None: 
 85          varargs = "_decorator__varargs" 
 86      return argnames, varargs, kwargs, defaults 
 87   
 88   
 89 -def compose(*decorators): 
 90      """Compose decorators.""" 
 91      return lambda func: reduce(lambda f, g: g(f), decorators, func) 
 92   
 93   
 94 -def func_composition(func): 
 95      """Return composition (decorator wise) of function.""" 
 96      return getattr(func, "__composition__", [func]) 
 97   
 98   
 99 -def func_original(func): 
100      """Return original (undecorated) function.""" 
101      return func_composition(func)[0] 
102   
103   
104 -def func_id(func): 
105      """Return identity of function. 
106   
107      If decorator was created with decorator() or weak_signature_decorator(), 
108      identity is invariant under decorator application. 
109   
110      """ 
111      return id(func_original(func)) 
112   
113   
114 -def func_eq(f, g): 
115      """Check if functions are identical.""" 
116      return func_id(f) == func_id(g) 
117