python eval inside a class

Question

I have to write a lot of Python code which will look like the following:

class MyClass(object):
    ...
    ...
    ...
    def handle_request(self, request):
        attr1 = self.__get_attr1(request)
        self.__validate_attr1(attr1)

        attr2 = self.__get_attr2(request)
        self.__validate_attr2(attr2)

        attr3 = self.__get_attr3(request)
        self.__validate_attr1(attr3)
        ...
        ...
        ...
        attrn = self.__get_attrn(request)
        self.__validate_attrn(attr1)

To make my life easier I thought I could do the following:

class MyClass(object):
    ...
    ...
    ...
    def handle_request(self, request):
        attr_list = ('attr1', 'attr2', 'attr3', ..., 'attrn');
        for a in attr_list:
            locals()[a] = eval('self.__get_{}(request)'.format(a))
            eval('self.__validate_{}'.format(a)

However when I run this code I'm getting a following error:

AttributeError: 'MyClass' object has no attribute '__get_attr1'

Clearly I'm missing something big but I'm not sure what exactly.

You clearly haven't defined the value of __get_attr1 before using it. — Ébe Isaac
– Ébe Isaac, Commented Dec 11, 2016 at 4:21
I may, but too bad your program couldn't do the same. Could you access __get_attr1 by any other means outside eval? — Ébe Isaac
– Ébe Isaac, Commented Dec 11, 2016 at 4:31
Like simply printing it before using eval, print(self.__get_attr1) — Ébe Isaac
– Ébe Isaac, Commented Dec 11, 2016 at 4:46

Iluvatar · Accepted Answer · 2016-12-11 04:30:38Z

1

To answer the question you didn't ask, instead of using eval, you might try something like

class MyClass(object):
    ...
    def __init__(self):
        self.attr_list = [self.__get_attr1, ..., self.__get_attrn]
        self.validate_list = [self.__validate_attr1, ..., self.__validate_attrn]
    ...
    def handle_request(self, request):
        attrs = [get(request) for get in self.attr_list]
        for validate in self.validate_list:
            validate(request)

answered Dec 11, 2016 at 4:30

Iluvatar

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1 Comment

Klaus D. Over a year ago

Or just getattr(self, attribute_name).

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