Getting an object property via a string name of the property in Python

Question

In the following code data_var is my object from a Django query, i.e. data_var = Datavar.objects.all(). I have database fields like field1, field2, field3, etc. In the following code I am trying to get the name of the field as a string in var and then say tg.var but I get an error as object has no attribute 'var':

If I say tg.var it should be interpreted as tg.field1 or 2 or 3. How to achieve this?

for tg in data_var:
     for col in range(content.no_of_cols):
        var = "field" + str(col)
        tg.var

Can you clarify what your expected output should be? An example would be nice. — thegrinner
– thegrinner, Commented Aug 9, 2012 at 12:12
i have hight lighted it.tg.var should be assumed as tg.field1 etc.... — Rajeev
– Rajeev, Commented Aug 9, 2012 at 12:13

Rostyslav Dzinko · Accepted Answer · 2014-03-03 16:57:09Z

8

To get object's attribute with a string name you should use getattr built-in function, and that way transforms your code to the next lines:

for tg in data_var:
     for col in range(content.no_of_cols):
        var = "field" + str(col)
        value = getattr(tg, var)

gettatr is explained in Python doc.

edited Mar 3, 2014 at 16:57

answered Aug 9, 2012 at 12:19

Rostyslav Dzinko

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Comments

aneroid · Accepted Answer · 2012-08-09 12:36:18Z

1

Looks like you're trying variable variables like in PHP. Python doesn't have it. You need to use a dictionary or getattr.

(Edit-ing since the first answer already covers getattr).

You can also refer to it from the dict:

>>> var = 'field1'
>>> tg.__dict__[var]
'this is field1'
>>> var = 'field2'
>>> tg.__dict__[var]
'this is field2'
>>> getattr(tg, var)
'this is field2'

edited Aug 9, 2012 at 12:36

answered Aug 9, 2012 at 12:26

aneroid

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