Creating an empty object with nested attributes in Python

Question

I'm trying to create an empty object which contains nested attributes like this:

form = type('', (), {})()
form.foo.data = ''

But I get following attribute error:

>>> form = type('', (), {})()
>>> form.foo.data = ''
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'str' object has no attribute 'data'

How should I construct the object to accomplish that?

Well the class constructor would be the Form class from WTForms. But in this case I only want to create a 'fake' object which only contains those attributes: form.foo.data or form.bar.data and so on. — ericMTR
– ericMTR, Commented Dec 9, 2016 at 12:46
@Navidad20 It's for a test case. I need to assign the values to those attributes manually. — ericMTR
– ericMTR, Commented Dec 9, 2016 at 12:54

Navidad20 · Accepted Answer · 2016-12-09 12:55:49Z

3

As per the type function , the third argument should be in the form of dictionary. So, for nested attributes, you can create the object before itself and then use it in the dictionary. Something like this might work -

da = type('',(),{'data':1})    
a = type('',(),{'foo':da})

edited Dec 9, 2016 at 12:55

Navidad20

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answered Dec 9, 2016 at 12:53

Raja Sudhan

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1 Comment

Rodrigo Moraes Over a year ago

This way looks good, but I think we have a "better" way to do this with MagicMock, like in this

metmirr · Accepted Answer · 2016-12-09 13:00:34Z

0

I dont get your point but you may use namedtuple :

>>>from collections import namedtuple

>>>foo = namedtuple('foo', "data tuple dict")
>>>foo.data = ""
''
>>> foo.tuple = ()
>>> foo.tuple
()

answered Dec 9, 2016 at 13:00

metmirr

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