How to create 'empty' object with desired field

Question

For test purposes I need to create something like an empty object with some particular fields. Let me clarify by example:

Currently there is a structure:

var = {
    'blas': {
        'bla':       0.250,
        'bla1':        0.300,
        'bla2': 6,
        ...
    },
    'somth1': self.smth1,
    'something': [
        { 'h1': 66.00 },
        { 'h2': 47.00 },
        { 'h3': 85.00 },
        { 'h4': 32.00 },
        { 'h5': 34.00 }
    ],
    'this_has_to_be_object'.field: 1
}

The thing I want is for 'this_has_to_be_object' to be an actual object to which I can add some fields and set values. The objective of such behaviour is to test another function that operates with 'this_has_to_be_object'.field.

Answer 1

Namedtuples are on way, if they don't have to be mutable:

from collections import namedtuple

MyTupleType = namedtuple('MyTupleType', ['field'])

yourobject = MyTupleType(field=3)

print(yourobject.field)  # prints 3

If it's for testing, then using the Mock library is also handy (see http://www.voidspace.org.uk/python/mock/ ; unittest.mock is part of the standard library since Python 3.3 as well).

yourobject = MagicMock()
yourobject.field = 3

Note that yourobject now has any field or method you try to access on it, and their values are all yet another MagicMock instance. It's a very powerful unit testing tool.

Lastly you can just create a boring dummy class:

class Dummy(object):
    pass

yourobject = Dummy()
yourobject.field = 3

Answer 2

Why not use a Default dict here.e.g.

var  = defaultdict(int)

var.update({
    'blas': {
        'bla':       0.250,
        'bla1':        0.300,
        'bla2': 6,
        ...
    },
    'somth1': self.smth1,
    'something': [
        { 'h1': 66.00 },
        { 'h2': 47.00 },
        { 'h3': 85.00 },
        { 'h4': 32.00 },
        { 'h5': 34.00 }
    ],
    'this_has_to_be_object'.field: 1
}
)

Now var['anything'] would always return with 0.

I guess that is the functionality you require for testing, Right ?

Answer 3

var = {
'blas': {
    'bla':       0.250,
    'bla1':        0.300,
    'bla2': 6,
    ...
},
'somth1': self.smth1,
'something': [
    { 'h1': 66.00 },
    { 'h2': 47.00 },
    { 'h3': 85.00 },
    { 'h4': 32.00 },
    { 'h5': 34.00 }
],
'this_has_to_be_object':{'field': '1'}

}

this is already a object, if you said you want to add some field inside you can do it like

...this_has_to_be_object.newField = 3; 

isn't this what you want?