For loop with object's attributes in Python

Question

I am working with objects in Python and all I wanted was to replace the attribute in a for loop to get the data out of the object. Here is my code:

def calculate_something(dictionaryWithObjects):
    for attribute in ['attr1', 'attr2', 'attr3']:
        dataA1, dataA2 = dictionaryWithObjects['Object1'].attribute
        dataB1, dataB2 = dictionaryWithObjects['Object2'].attribute
        dataC1, dataC2 = dictionaryWithObjects['Object3'].attribute

So this is more or less what I think I need. I will use the data for calculations afterwards. But it gives an error saying that the object has no attribute called ".attribute". Of course it doesn't, I meant it to replace the 'attr1' in there.

What am I doing wrong?

Take a look at getattr / setattr (https://docs.python.org/3/library/functions.html#setattr) — awesoon, Apr 20 '18 at 06:35
You're looking for `getattr`, `getattr(dictionary['Obj1'], attribute)` — Taku, Apr 20 '18 at 06:35
`.attribute` is not a variable there, so you can not replace that with the real variable `attribute` in your for loop. — BcK, Apr 20 '18 at 06:35
Since you are learning, once you have the `getattr` working, what happens if you remove the `[` `]` from the series of attribute names in the `for`? — cdarke, Apr 20 '18 at 06:37
Possible duplicate of [A get() like method for checking for Python attributes](https://stackoverflow.com/questions/355539/a-get-like-method-for-checking-for-python-attributes) — CristiFati, Apr 20 '18 at 06:41

score 4 · Accepted Answer · answered Apr 20 '18 at 06:34

4

In order to access an instance attribute by its name, you should use [Python]: getattr(object, name[, default]), e.g.:

dataA1, dataA2 = getattr(dictionaryWithObjects['Object1'], attribute)

answered Apr 20 '18 at 06:34

CristiFati

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does the dictionaryWithObjects.get("Object1",attribute) have same as u answered – Roushan Apr 20 '18 at 06:36
@Roushan: True, but that wasn't part of the question, and I didn't want to overcomplicate the answer. – CristiFati Apr 20 '18 at 06:37
@Roushan: Only now I understood what you mean by your 1st comment. I thought it was replacing the `[]` by the `get` method. – CristiFati Apr 20 '18 at 06:46

score 0 · Answer 2 · edited Apr 20 '18 at 06:38

0

Try something like this:

def calculate_something(dictionaryWithObjects):
    for attribute in ['attr1', 'attr2', 'attr3']:
        dataA1, dataA2 = dictionaryWithObjects['Object1'][attribute]

edited Apr 20 '18 at 06:38

cdarke

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answered Apr 20 '18 at 06:36

NoorJafri

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this doen't work because the attribute is not a key.. It's an object. I've tried that in the beggining x) – Bella Apr 20 '18 at 06:39
Well can you paste the result for dir(dictionaryWithObjects) and dir(dictionaryWithObjects["Object1"]. This actually helps to get you with your loops over your whatever. – NoorJafri Apr 20 '18 at 06:44
@NoorAliJafri you would generally want to use `vars` instead of `dir`, but why would you, if you can just us `getattr`? – juanpa.arrivillaga Apr 20 '18 at 07:06
@juanpa.arrivillaga I was letting her know to use python's cli with dir(yourobject) to have a better picture of the variable. That's it :D – NoorJafri Apr 20 '18 at 07:17

Artemis · Answer 3 · 2018-04-20T19:19:55.330

0

You can use eval:

data=eval('Object1.'+attribute)

edited Apr 20 '18 at 19:19

answered Apr 20 '18 at 06:58

Artemis

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Doesn't work (in the question context), but even if it did, it would be one of the ugliest and avoidable ways. – CristiFati Apr 20 '18 at 08:19
Because your code snippet doesn't fit in the question context (where there's no "Obj"). – CristiFati Apr 20 '18 at 15:35
I've changed it, however the point of SO questions is to also solve problems for future users, so it makes no sense to be entirely context specific. – Artemis Apr 20 '18 at 19:19

For loop with object's attributes in Python

3 Answers3