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Not sure if this the recommended way of doing things in Python. I have a class with a bunch of attributes, like so

class MyClass:
    def __init__(self):
        self.attr1 = "first_value"
        self.attr2 = "second_value"
        ...

However, this is tedious, I want to be able to do this in a loop:

self.attr_list = ["attr1", "attr2", "another_attr",...]

def __init__(self, values_list):
    self.attr_values = [some_func(i) for i in values_list]

But I also later want to call these values like so: 

foo = MyClass(values_list)
...

bar = foo.attr1

myFunc(foo.another_attr, ..., some_other_parameters)

So the question is, how do I avoid the tedious first method where the line for each attribute is hard-coded, but still get the convenience of referring to an attribute without having to know/remember where in the list it is?

Hope this is clearer.

Thanks

P.S. I'm using Python 3

Samuel Tan
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1 Answers1

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I'm not sure I understand the question. Are you looking for setattr? Something like this:

def assign(self, attr_names, value_list):
    for i in range(len(attr_names)):
        setattr(self, attr_names[i], some_func(value_list[i]))

You can use it like that:

foo.assign(["attr1", "attr2"], value_list)    
print(foo.attr1)

I don't think that using setattr is wrong per se however I advice using dictionaries instead since you might overwrite other attributes by accident, for example consider this:

foo.assign(["assign"], [1])
foo.assign(["assign"], [1])  # <-- exception now
freakish
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  • And using dictionaries would avoid overwriting existing attributes? – Samuel Tan Apr 11 '14 at 13:21
  • Thank you, I managed to try both `setattr` and dictionaries and they are both solutions. At the moment, I'm only setting these values once, in `__init__`, so I won't be overwriting them. – Samuel Tan Apr 11 '14 at 13:50
  • @SamuelTan What I've meant is that you keep a dictionary attribute, i.e. `foo.my_dict = {}` in `__init__` and then you assign to that dictionary. That way you avoid accidental overwrites. – freakish Apr 11 '14 at 13:51