Adding variably named fields to Python classes

Question

I have a python class, and I need to add an arbitrary number of arbitrarily long lists to it. The names of the lists I need to add are also arbitrary. For example, in PHP, I would do this:

class MyClass {

}

$c = new MyClass();
$n = "hello"
$c.$n = array(1, 2, 3);

How do I do this in Python?

I'm also wondering if this is a reasonable thing to do. The alternative would be to create a dict of lists in the class, but since the number and size of the lists is arbitrary, I was worried there might be a performance hit from this.

If you are wondering what I'm trying to accomplish, I'm writing a super-lightweight script interpreter. The interpreter walks through a human-written list and creates some kind of byte-code. The byte-code of each function will be stored as a list named after the function in an "app" class. I'm curious to hear any other suggestions on how to do this as well.

wRAR · Accepted Answer · 2010-05-05 04:35:11Z

5

Use setattr.

>>> class A(object):
...     pass
... 
>>> a = A()
>>> f = 'field'
>>> setattr(a, f, 42)
>>> a.field
42

answered May 5, 2010 at 4:35

wRAR

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Comments

jcolebrand · Accepted Answer · 2010-05-05 04:34:15Z

1

I would write it the simplest way for now, and profile next, and then look to optimize specific elements.

Let's remember the KISS principle.

answered May 5, 2010 at 4:34

jcolebrand

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2 Comments

jcolebrand Over a year ago

lol, sure, but I just wanted to clarify, it sounds like you're still in the dreaming stage, so I would wait till you've got a working prototype because this sounds like a specific optimization. The dict list is fine.

Carson Myers Over a year ago

I have some mock classes and I'm gradually filling them out. I was at the stage where I was figuring out how to hold the compiled data of a script. But really, so far I've done far more thinking and dreaming than code, because there's threads involved and I'm trying not to blow my foot off :)

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