从只需要搜索/替换字符串的模板生成 python 方法答案

【问题标题】：Generate python methods from template requiring mere search/replace of string从只需要搜索/替换字符串的模板生成 python 方法
【发布时间】：2016-10-13 06:26:25
【问题描述】：

这些天我正在使用 ANTLR 来解析一些语言。我选择使用 Python。 ANTLR 生成的解析器类包含许多名称相似的方法：

class autogeneratedparser(xxx):
    def something_enter(self,ctx):
       pass
    def something_exit(self,ctx)
       pass

我通过定义一个继承类来覆盖这些

class myclass(autogeneratedparser)
    particularthing = False
    def particularthing_enter(self,ctx):
       print(ctx.name)
       myclass.particularthing = true
    def particularthing_exit(self,ctx):
       print(ctx.name)
       myclass.particularthing = false

我想动态地自动生成所有这些方法，包括更改它们各自的变量名。在伪代码中：

generate for particularthing in anything:
        $(particularthing) = False
        def $(particularthing)_enter(self,ctx):
           print(ctx.name)
           myclass.$(particularthing) = true
        def $(particularthing)_exit(self,ctx):
           print(ctx.name)
           myclass.$(particularthing) = false

我显然可以告诉 vim 这样做，但我确信 Python 也有办法，只是不知道怎么做 :-)

感谢您的宝贵意见 :)

【问题讨论】：

标签： python dynamic methods lambda

【解决方案1】：

您需要做的就是遍历初始类的属性，只选择匹配SOMETHING_enter 和SOMETHING_exit 的那些，然后创建存根方法并将它们与type() (yes, it is used for creating dynamic classes) 放在一起。

这是我的版本：

# the generated class
class SomeClass(object):
    def something_enter(self, ctx):
       pass
    def something_exit(self, ctx):
       pass


def generate_stubbed_class(klass_name, klass):
    # creates and returns a function that does the generic behavior (print's out ctx.name)
    # and sets the attribute to the given value
    def generate_stub(name, value):
        def stub(self, ctx):
            print(ctx.name)
            setattr(self, name, value)

        return stub

    attributes = {}

    for name in dir(klass): # lists all attributes (names only)
        try:
            key, oper = name.split('_')
        except ValueError:
            # not in the format of SOMETHING_SOMETHING
            continue

        attr = getattr(klass, name)

        # make sure it's a function and name ends in _enter or _exit
        if callable(attr) and oper in ('enter', 'exit'):
            value = oper == 'enter' # True for 'enter', False for 'exit'
            attributes[name] = generate_stub(key, value)
            attributes[key] = False # set more than once, but no negative effect

    # this is where the magic happens
    return type(klass_name, (klass,), attributes)


MyClass = generate_stubbed_class('MyClass', SomeClass)
obj = MyClass()

assert isinstance(obj, SomeClass)

# need some class with a 'name' attribute, so we create one on the fly
from collections import namedtuple
Data = namedtuple('Data', 'name')

# initially it's False
assert obj.something is False

# set to True, prints 'foo'
obj.something_enter(Data('foo'))
assert obj.something is True

# back to False, prints 'bar'
obj.something_exit(Data('bar'))
assert obj.something is False

【讨论】：