装饰器定义为类#
场景
此装饰器可以用在类/函数中也可以用于类/函数外。
from types import MethodType
from typing import Any
from functools import wraps
class Profiled:
def __init__(self, func):
wraps(func)(self)
self.ncalls = 0
def __call__(self, *args, **kwds):
self.ncalls += 1
return self.__wrapped__(*args, **kwds)
def __get__(self, obj, objtype=None):
if obj is None:
return self
else:
return MethodType(self, obj)
可以用于装饰函数：
@Profiled
def add(x, y):
return x + y
print(add.ncalls) # 函数外使用
a = add(2, 3)
print(add.ncalls)
a = add(4, 5)
print(add.ncalls)
0
1
2
可以用于装饰类：
class Spam:
@Profiled
def bar(self, x):
print(self, x)
s = Spam()
print(Spam.bar.ncalls) # 类外使用
a = s.bar(1)
print(Spam.bar.ncalls)
a = s.bar(2)
print(s.bar.ncalls)
0
<__main__.Spam object at 0x7fe898f40cb0> 1
1
<__main__.Spam object at 0x7fe898f40cb0> 2
2
此 Profiled 记录了函数或类的调用次数。
记录中间结果#
from types import MethodType
from typing import Any
from functools import wraps
from weakref import WeakValueDictionary
class Cached(type):
def __init__(self, *args, **kwds):
super().__init__(*args, **kwds)
self.__cache = WeakValueDictionary()
def __call__(self, *args, **kwds):
if args in self.__cache:
return self.__cache[args]
else:
obj = super().__call__(*args, **kwds)
self.__cache[args] = obj
print("1", args, kwds)
return obj
class ProfiledAccess:
cache = {}
is_activate = False
def __init__(self, func, *cargs, **ckwds):
super().__init__(*cargs, **ckwds)
self.ncalls = 0 # 调用次数
self.varname = "temp"
wraps(func)(self)
def __call__(self, *args, **kwds):
func = self.__wrapped__
values = func(*args, **kwds)
if type(self).is_activate:
type(self).cache[func.__qualname__] = values
self.ncalls += 1
return values
def __get__(self, obj, objtype=None):
if obj is None:
return self
else:
return MethodType(self, obj)
@classmethod
def activate(cls):
cls.is_activate = True
@classmethod
def clear(cls):
cls.cache.clear()
from bytecode import Bytecode, Instr
class Profiled:
def __init__(self, func):
self.varname = "return"
wraps(self.transform(func))(self, self.varname)
self.ncalls = 0
def transform(self, func):
"""修改函数返回值为：(原返回值, varname表示的值)
"""
c = Bytecode.from_code(func.__code__)
extra_code = [
Instr('STORE_FAST', '_res'),
Instr('LOAD_FAST', self.varname),
Instr('STORE_FAST', '_value'),
Instr('LOAD_FAST', '_res'),
Instr('LOAD_FAST', '_value'),
Instr('BUILD_TUPLE', 2),
Instr('STORE_FAST', '_result_tuple'),
Instr('LOAD_FAST', '_result_tuple'),
]
c[-1:-1] = extra_code
func.__code__ = c.to_code()
return func
def __call__(self, *args, **kwds):
self.ncalls += 1
return #self.__wrapped__(*args, **kwds)
# def __get__(self, obj, objtype=None):
# if obj is None:
# return self
# else:
# return MethodType(self, obj)
def func(x, y):
c = x + y
return c ** 2
varname = "c"
cache = WeakValueDictionary()
func(2, 3)
25
其他#
a = Spam(2)
b = Spam(3)
c = Spam(2)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
Cell In[13], line 1
----> 1 a = Spam(2)
2 b = Spam(3)
3 c = Spam(2)
TypeError: Spam() takes no arguments
a is c
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
Cell In[14], line 1
----> 1 a is c
NameError: name 'c' is not defined
exec("b = a + 1")
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
Cell In[15], line 1
----> 1 exec("b = a + 1")
File <string>:1
TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'
print(b)
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
Cell In[16], line 1
----> 1 print(b)
NameError: name 'b' is not defined
def test():
a = 13
loc = locals()
exec("b = a + 1")
print(loc["b"])
test()
14
def test():
x = 13
loc = locals()
exec("x += 1")
print(x)
print(loc)
test()
13
{'x': 14, 'loc': {...}}
x = 42
eval()
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
Cell In[22], line 1
----> 1 eval()
TypeError: eval expected at least 1 argument, got 0
exec("for k in range(10): print(k)")
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import ast
ex = ast.parse("2 + 3*4 + x", mode="eval")
print(ast.dump(ex))
Expression(body=BinOp(left=BinOp(left=Constant(value=2), op=Add(), right=BinOp(left=Constant(value=3), op=Mult(), right=Constant(value=4))), op=Add(), right=Name(id='x', ctx=Load())))
import ast
class CodeAnalyzer(ast.NodeVisitor):
def __init__(self) -> None:
super().__init__()
self.loaded = set()
self.stored = set()
self.deleted = set()
def visit_Name(self, node):
if isinstance(node.ctx, ast.Load):
self.loaded.add(node.id)
elif isinstance(node.ctx, ast.Store):
self.stored.add(node.id)
elif isinstance(node.ctx, ast.Del):
self.deleted.add(node.id)
code = """
for k in range(10):
print(k)
del k
"""
top = ast.parse(code, mode="exec")
c = CodeAnalyzer()
c.visit(top)
c.loaded
{'k', 'print', 'range'}
c.stored
{'k'}
c.deleted
{'k'}
exec(compile(top, "<stdin>", "exec"))
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