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 (docs.python.org/3/library/functions.html#setattr) — awesoon
– awesoon, Commented Apr 20, 2018 at 6:35
You're looking for getattr, getattr(dictionary['Obj1'], attribute) — Taku
– Taku, Commented Apr 20, 2018 at 6:35
.attribute is not a variable there, so you can not replace that with the real variable attribute in your for loop. — BcK
– BcK, Commented Apr 20, 2018 at 6:35
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
– cdarke, Commented Apr 20, 2018 at 6:37
Possible duplicate of A get() like method for checking for Python attributes — CristiFati
– CristiFati, Commented Apr 20, 2018 at 6:41

CristiFati · Accepted Answer · 2018-04-20 06:34:54Z

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, 2018 at 6:34

CristiFati

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3 Comments

Roushan Over a year ago

does the dictionaryWithObjects.get("Object1",attribute) have same as u answered

CristiFati Over a year ago

@Roushan: True, but that wasn't part of the question, and I didn't want to overcomplicate the answer.

CristiFati Over a year ago

@Roushan: Only now I understood what you mean by your 1st comment. I thought it was replacing the [] by the get method.

cdarke · Accepted Answer · 2018-04-20 06:38:15Z

0

Try something like this:

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

edited Apr 20, 2018 at 6:38

cdarke

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answered Apr 20, 2018 at 6:36

NoorJafri

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4 Comments

Bella Over a year ago

this doen't work because the attribute is not a key.. It's an object. I've tried that in the beggining x)

NoorJafri Over a year ago

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.

juanpa.arrivillaga Over a year ago

@NoorAliJafri you would generally want to use vars instead of dir, but why would you, if you can just us getattr?

NoorJafri Over a year ago

@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

Miriam · Accepted Answer · 2018-04-20 19:19:55Z

0

You can use eval:

data=eval('Object1.'+attribute)

edited Apr 20, 2018 at 19:19

answered Apr 20, 2018 at 6:58

Miriam

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3 Comments

CristiFati Over a year ago

Doesn't work (in the question context), but even if it did, it would be one of the ugliest and avoidable ways.

CristiFati Over a year ago

Because your code snippet doesn't fit in the question context (where there's no "Obj").

Miriam Over a year ago

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.

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