Conditionally Add An Attribute To An Dictionary in Python

Question

I want to be able to add an attribute to a dictionary but only if the condition I pass in is true. For example:

def addSum(num):
    obj = {
             'name': "Home",
              'url': "/",
              num > 0 ? 'data': num
    }

Is this possible? I can't find a way to do this in python, I have only seen examples in javascript.

Can you add the javascript equivalent that you had in mind as well? What you posted is not valid js. Don't know of any similar syntax in javascript but it would be cool :) — André Laszlo, Jun 27 '19 at 20:13
lots of examples on here, here is one https://stackoverflow.com/questions/11704267/in-javascript-how-to-conditionally-add-a-member-to-an-object/38483660 — Demetrius, Jun 27 '19 at 20:16

Prune · Accepted Answer · 2019-06-28T16:41:05.877

6

You can't do it with quite that syntax. For one thing, you need Python, not Java/C.

(1) add the attribute, but set to None:

obj = {'name': "Home",
       'url': "/",
       'data': num if num > 0 else None
      }

(2) make it an add-on:

obj = {'name': "Home",
       'url': "/"}
if num > 0:
    obj['data'] = num

edited Jun 28 '19 at 16:41

answered Jun 27 '19 at 20:13

Prune

76,765
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So in the first example the condition has to go after the value? – Demetrius Jun 27 '19 at 20:20
1

Yes. See any tutorial on the Python ternary operator. – Prune Jun 27 '19 at 20:25
the 1st example will throw SyntaxError – RomanPerekhrest Jun 28 '19 at 05:48
Thanks; fixed the missing quotation mark and tested with cut-and-paste. – Prune Jun 28 '19 at 16:42

score 3 · Answer 2 · answered Jun 27 '19 at 20:12

Just add/check it in separate statement:

def addSum(num):
    obj = {
        'name': "Home",
        'url': "/"
    }
    if num > 0: obj['data'] = num
    return obj

print(addSum(3))   # {'name': 'Home', 'url': '/', 'data': 3}
print(addSum(0))   # {'name': 'Home', 'url': '/'}

score 3 · Answer 3 · answered Feb 28 '23 at 15:43

3

obj = {
    'name': 'Home',
    'url': '/',
    **({'data': num} if num > 0 else {})
}

:D

answered Feb 28 '23 at 15:43

MaxCore

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score 2 · Answer 4 · answered Jun 27 '19 at 20:12

2

Create the dictionary without the optional element, then add it in an if statement

def addSum(num):
    obj = {
        'name': "Home",
        'url': "/"
    }
    if num > 0:
        obj['data'] = num;

answered Jun 27 '19 at 20:12

Barmar

741,623
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score 2 · Answer 5 · answered Jun 27 '19 at 20:13

Yes, just create the dictionary without the attribute, then create an if statement to add it if the condition is true:

def addSum(num):
    obj = {
          'name': "Home",
          'url': "/",      
    }
    if num > 0:
        obj['data'] = num

    return obj

Conditionally Add An Attribute To An Dictionary in Python

5 Answers5