How to know if something exists in a dictionary in python

Question

I'm consuming an API and the info from it would be something like this:

"id": "17",
"address": "Av. Nossa Senhora de Copacabana",
"addressComplement": "A",
"number": "945",
"cityId": "2",
"cityName": "Rio de Janeiro",
"state": "Rio de Janeiro",
"uf": "RJ",
"neighborhood": "Copacabana",
"properties": {},
"telephones": [],
"geolocation": {
    "lat": -22.97625,
    "lng": -43.19002
},

But, in some records, it doesn't contain the geolocation field, so I have to check if geolocation exists inside my code.

I was trying to use hasattr to do this trick, but I think I'm doing something wrong.

Here is the part of my code:

if hasattr(i, 'geolocation'):
    address_lat = i['geolocation']['lat']
    address_lng = i['geolocation']['lng']
else:
    address_lat = 0.0
    address_lng = 0.0

My thought here is that it will check if in the position of index i exist something inside geolocation. If there is something, then it returns true and enter inside the condition, else the var will receive 0.0.

So, am I doing something wrong? Is this the right way to use hasattr?

Possible duplicate of [Check if a given key already exists in a dictionary](https://stackoverflow.com/questions/1602934/check-if-a-given-key-already-exists-in-a-dictionary) — TrebledJ, Feb 19 '19 at 11:10
You shouldn't use `0.0` for missing values. It's a valid lat-lng; `np.nan` or an out of range number (say, 1000) is probably much more appropriate. — suvayu, Feb 19 '19 at 14:24

Óscar López · Accepted Answer · 2019-02-19T11:07:13.073

10

It's simpler than that:

address_lat = i['geolocation']['lat'] if 'geolocation' in i else 0.0
address_lng = i['geolocation']['ing'] if 'geolocation' in i else 0.0

hasattr is useful for checking if an object has an attribute. This is a more specific case, you just need to check if a key is in a dictionary.

A minor complaint: i is a confusing name for a dictionary, at first sight I thought that was an index. Better rename it to something meaningful!

edited Feb 19 '19 at 11:07

answered Feb 19 '19 at 11:05

Óscar López

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`.get()` you mean? – Chris_Rands Feb 19 '19 at 11:06
2

If 'geolocation' does not exist in `i`at all this would nevertheless raise a KeyError? – sebastian Feb 19 '19 at 11:06
yup, I just realised that. It's fixed now, thanks for pointing that out! – Óscar López Feb 19 '19 at 11:07

score 9 · Answer 2 · answered Feb 19 '19 at 11:09

9

You could use the dict.get method that allows to supply a default value that will be returned if the key does not exist, e.g. like:

geolocation = i.get('geolocation', {"lat": 0., "lng": 0.})

answered Feb 19 '19 at 11:09

sebastian

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removes the need for `try/except` or `if` check, +1 – RoadRunner Feb 19 '19 at 11:26

myusko · Answer 3 · 2019-02-19T11:41:32.267

1

hasattr is usually using for an object.

>>> class A:
...     i = 10
...
>>> hasattr(A(), 'i')
True

In your case, the best way to check if a key exists in a dictionary it's to do something like that

data = {'geolocation': 0.0}
if 'geolocation' in data:
     ...do something

edited Feb 19 '19 at 11:41

answered Feb 19 '19 at 11:07

myusko

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score 1 · Answer 4 · answered Feb 19 '19 at 11:11

1

You could use a try except clause:

try:
    address_lat = i['geolocation']['lat']
    address_lng = i['geolocation']['lng']
except KeyError:
    address_lat = 0.0
    address_lng = 0.0

answered Feb 19 '19 at 11:11

Valentino

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score 1 · Answer 5 · answered Feb 19 '19 at 13:12

1

You can use get and set the default values for lat and lng if they doesn't exist.

geolocation = i.get('geolocation',{"lat": 0,"lng":0})
address_lat = geolocation['lat']
address_lng = geolocation['lng']

answered Feb 19 '19 at 13:12

Gautam Kumar

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How to know if something exists in a dictionary in python

5 Answers5