如何让self进入Python方法而不显式接受它

这里有一个单行方法修饰符,它似乎不需要修改任何 Special attributes of Callable types* marked Read-only :

# method decorator -- makes undeclared 'self' argument available to method
injectself = lambda f: lambda self: eval(f.func_code, dict(self=self))

class TestClass:
    def __init__(self, thing):
        self.attr = thing

    @injectself
    def method():
        print 'in TestClass::method(): self.attr = %r' % self.attr
        return 42

test = TestClass("attribute's value")
ret = test.method()
print 'return value:', ret

# output:
# in TestClass::method(): self.attr = "attribute's value"
# return value: 42

side-effect eval() 函数可能是它添加了一些条目——比如对 __builtin__ 钥匙下的模块 __builtins__ dict 传递给它。

@kendall:根据您关于如何在容器类中使用这个方法的评论(但目前忽略了额外变量的注入)--下面的内容与您所做的类似吗?对于我来说,很难理解框架和用户编写的东西是如何分开的。我觉得这是一个有趣的设计模式。

# method decorator -- makes undeclared 'self' argument available to method
injectself = lambda f: lambda self: eval(f.func_code, dict(self=self))

class methodclass:
    def __call__():
        print 'in methodclass::__call__(): self.attr = %r' % self.attr
        return 42

class TestClass:
    def __init__(self, thing):
        self.attr = thing

    method = injectself(methodclass.__call__)

test = TestClass("attribute's value")
ret = test.method()
print 'return value:', ret

# output
# in methodclass::__call__(): self.attr = "attribute's value"
# return value: 42

add_self

import opcode
import types



def instructions(code):
    """Iterates over a code string yielding integer [op, arg] pairs

    If the opcode does not take an argument, just put None in the second part
    """
    code = map(ord, code)
    i, L = 0, len(code)
    extended_arg = 0
    while i < L:
        op = code[i]
        i+= 1
        if op < opcode.HAVE_ARGUMENT:
            yield [op, None]
            continue
        oparg = code[i] + (code[i+1] << 8) + extended_arg
        extended_arg = 0
        i += 2
        if op == opcode.EXTENDED_ARG:
            extended_arg = oparg << 16
            continue
        yield [op, oparg]


def write_instruction(inst):
    """Takes an integer [op, arg] pair and returns a list of character bytecodes"""
    op, oparg = inst
    if oparg is None:
        return [chr(op)]
    elif oparg <= 65536L:
        return [chr(op), chr(oparg & 255), chr((oparg >> 8) & 255)]
    elif oparg <= 4294967296L:
        # The argument is large enough to need 4 bytes and the EXTENDED_ARG opcode
        return [chr(opcode.EXTENDED_ARG),
                chr((oparg >> 16) & 255),
                chr((oparg >> 24) & 255),
                chr(op),
                chr(oparg & 255),
                chr((oparg >> 8) & 255)]
    else:
        raise ValueError("Invalid oparg: {0} is too large".format(oparg))


def add_self(f):
    """Add self to a method

    Creates a new function by prepending the name 'self' to co_varnames, and      
    incrementing co_argcount and co_nlocals. Increase the index of all other locals
    by 1 to compensate. Also removes 'self' from co_names and decrease the index of 
    all names that occur after it by 1. Finally, replace all occurrences of 
    `LOAD_GLOBAL i,j` that make reference to the old 'self' with 'LOAD_FAST 0,0'.   

    Essentially, just create a code object that is exactly the same but has one more
    argument. 
    """
    code_obj = f.func_code
    try:
        self_index = code_obj.co_names.index('self')
    except ValueError:
        raise NotImplementedError("self is not a global")

    # The arguments are just the first co_argcount co_varnames
    varnames = ('self', ) + code_obj.co_varnames   
    names = tuple(name for name in code_obj.co_names if name != 'self')

    code = []

    for inst in instructions(code_obj.co_code):
        op = inst[0]
        if op in opcode.haslocal:
            # The index is now one greater because we added 'self' at the head of
            # the tuple
            inst[1] += 1
        elif op in opcode.hasname:
            arg = inst[1]
            if arg == self_index:
                # This refers to the old global 'self'
                if op == opcode.opmap['LOAD_GLOBAL']:
                    inst[0] = opcode.opmap['LOAD_FAST']
                    inst[1] = 0
                else:
                    # If `self` is used as an attribute, real global, module
                    # name, module attribute, or gets looked at funny, bail out.
                    raise NotImplementedError("Abnormal use of self")
            elif arg > self_index:
                # This rewrites the index to account for the old global 'self'
                # having been removed.
                inst[1] -= 1

        code += write_instruction(inst)

    code = ''.join(code)

    # type help(types.CodeType) at the interpreter prompt for this one   
    new_code_obj = types.CodeType(code_obj.co_argcount + 1,
                                  code_obj.co_nlocals + 1,
                                  code_obj.co_stacksize,
                                  code_obj.co_flags, 
                                  code,
                                  code_obj.co_consts,
                                  names, 
                                  varnames, 
                                  '<OpcodeCity>',
                                  code_obj.co_name,  
                                  code_obj.co_firstlineno,
                                  code_obj.co_lnotab, 
                                  code_obj.co_freevars,
                                  code_obj.co_cellvars)


    # help(types.FunctionType)
    return types.FunctionType(new_code_obj, f.func_globals)



class Test(object):

    msg = 'Foo'

    @add_self
    def show(msg):
        print self.msg + msg


t = Test()
t.show('Bar')

aaronasterling的解决方案几乎没有升级(我没有足够的声誉来评论它):

def wrap(f):
    @functools.wraps(f)
    def wrapper(self,*arg,**kw):
        f.func_globals['self'] = self        
        return f(*arg,**kw)
    return wrapper

但这两种解决方案都无法预测,如果f函数将针对不同的实例递归调用,那么您必须像这样克隆它:

import types
class wrap(object):
    def __init__(self,func):
        self.func = func
    def __get__(self,obj,type):
        new_globals = self.func.func_globals.copy()
        new_globals['self'] = obj
        return types.FunctionType(self.func.func_code,new_globals)
class C(object):
    def __init__(self,word):
        self.greeting = word
    @wrap
    def greet(name):
        print(self.greeting+' , ' + name+ '!')
C('Hello').greet('kindall')

f.func_globals . 这在python2.6中有效。我真的应该去安装其他版本来测试像这样的东西。对不起,代码墙,但我涉及两种情况:使用元类和装饰器。对于您的用例,我认为元类更好,因为这个练习的重点是保护用户不受语法的影响。

import new, functools

class TestMeta(type):
    def __new__(meta, classname, bases, classdict):
        for item in classdict:
            if hasattr(classdict[item], '__call__'):
                classdict[item] = wrap(classdict[item])
        return type.__new__(meta, classname, bases, classdict)

def wrap(f):
    @functools.wraps(f)
    def wrapper(self):
        f.func_globals['self'] = self        
        return f()
    return wrapper

def testdec(f):
    @functools.wraps(f)
    def wrapper():
        return f()
    return wrapper

class Test(object):
    __metaclass__ = TestMeta
    message = 'You can do anything in python'
    def test():
        print self.message

    @testdec
    def test2():
        print self.message + ' but the wrapper funcion can\'t take a self argument either or you get a TypeError'

class Test2(object):
    message = 'It also works as a decorator but (to me at least) feels better as a metaclass'
    @wrap
    def test():
        print self.message


t = Test()
t2 = Test2()
t.test()
t.test2()
t2.test()

这可能是 decorators -你给他们一小套乐高积木来构建函数,复杂的框架材料通过管道输入 @testcase 或者类似的。

编辑: 您没有发布任何代码,所以这将是粗略的,但他们不需要编写方法。它们可以编写没有“self”的普通函数,您可以使用decorator,如我链接的文章中的示例所示:

class myDecorator(object):

    def __init__(self, f):
        print "inside myDecorator.__init__()"
        f() # Prove that function definition has completed

    def __call__(self):
        print "inside myDecorator.__call__()"

@myDecorator
def aFunction():
    print "inside aFunction()"