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== Counting function calls == {{{ class countcalls(object): "Decorator that keeps track of the number of times a function is called." __instances = {} def __init__(self, f): self.__f = f self.__numCalls = 0 countcalls.__instances[f] = self def __call__(self, *args, **kwargs): self.__numCalls += 1 return self.__f(*args, **kwargs) @staticmethod def count(f): "Return the number of times the function f was called." return countcalls.__instances[f].__numCalls @staticmethod def counts(): "Return a dict of {function: # of calls} for all registered functions." return dict([(f, countcalls.count(f)) for f in countcalls.__instances]) }}} |
This page is meant to be a central repository of decorator code pieces, whether useful or not <wink>. It is NOT a page to discuss decorator syntax!
Feel free to add your suggestions (please use the current decorator syntax @dec)!
Memoize
Here's a memoizing class.
inline:memoize.py
Pseudo-currying
Toggle line numbers
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)
Controllable DIY debug
(Other hooks could be similarly added. Docstrings and exceptions are left out for simplicity of demonstration.)
Toggle line numbers
1 import sys, sets
2
3 WHAT_TO_DEBUG = sets.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 = sets.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))
Easy adding methods to a class instance
Credits to John Roth.
Toggle line numbers
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"
Counting function calls
class countcalls(object):
"Decorator that keeps track of the number of times a function is called."
__instances = {}
def __init__(self, f):
self.__f = f
self.__numCalls = 0
countcalls.__instances[f] = self
def __call__(self, *args, **kwargs):
self.__numCalls += 1
return self.__f(*args, **kwargs)
@staticmethod
def count(f):
"Return the number of times the function f was called."
return countcalls.__instances[f].__numCalls
@staticmethod
def counts():
"Return a dict of {function: # of calls} for all registered functions."
return dict([(f, countcalls.count(f)) for f in countcalls.__instances])