How to check if an object exist in python

Question

I have a script to get data from an URL and transform into a JSON file. I have two items that I'm interested.

This is an example of what they return:

"images": [
        {
            "type": "PosterPortrait", 
            "url": "https://ingresso-a.akamaihd.net/img/cinema/cartaz/22454-cartaz.jpg"
        }, 
        {
            "type": "PosterHorizontal", 
            "url": "https://ingresso-a.akamaihd.net/img/cinema/cartaz/22454-destaque.jpg"
        }
    ], 

"trailers": [
        {
            "embeddedUrl": "//www.youtube.com/embed/YUBBkz5ZbKY", 
            "type": "Youtube", 
            "url": "https://www.youtube.com/watch?v=YUBBkz5ZbKY"
        }, 
        {
            "embeddedUrl": "//www.youtube.com/embed/YUBBkz5ZbKY", 
            "type": "Youtube", 
            "url": "https://www.youtube.com/watch?v=YUBBkz5ZbKY"
        }
    ],

I need to get the "url" and "type" from each object to save into a Postgresql database OneToMany - movie(One):media(Many). The problem is that "trailers" could be empty and I don't need to save it, since there isn't any data.

code.py

if(i['trailers']):
    a = [
        {'url': i['images'][0]['url'], 'type': i['images'][0]['type']},
        {'url': i['images'][1]['url'], 'type': i['images'][1]['type']},
        {'url': i['trailers'][0]['url'], 'type': 'Trailer'},
        {'url': i['trailers'][1]['url'], 'type': 'Trailer'},
    ] 
else:
    a = [
        {'url': i['images'][0]['url'], 'type': i['images'][0]['type']},
        {'url': i['images'][1]['url'], 'type': i['images'][1]['type']},
    ]

Here is my code. I'm trying to check if there's any elements inside of i['trailers']. If so, he'll be stored inside a dictionary.

Someone could help me to check this, please? Thanks!

Not really following fully, but use if (i.get('trailers')), which won't throw an error on a missing key; it will instead return None, which is falsey. — roganjosh
– roganjosh, Commented Dec 27, 2018 at 22:42
@roganjosh TypeError: 'builtin_function_or_method' object is not subscriptable — random2137
– random2137, Commented Dec 27, 2018 at 22:45
Wut...? :P either you misimplemented my suggestion, you have trampled some built-in or I'm overly tired. Please show the full traceback. — roganjosh
– roganjosh, Commented Dec 27, 2018 at 22:47

minboost · Accepted Answer · 2018-12-28 00:05:55Z

2

If trailers returns an empty list, and images is always not empty, you can replace all your code with one line using a list comprehension:

a = [{'url': x['url'], 'type': x['type']} for x in i['images'] + i['trailers']]

If trailers may be missing or None (instead of an empty list), you just add this line before it:

i['trailers'] = i.get('trailers') or []

edited Dec 28, 2018 at 0:05

answered Dec 27, 2018 at 22:51

minboost

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10 Comments

roganjosh Over a year ago

i['trailers'] = i.get('trailers', [])

minboost Over a year ago

@roganjosh that won't work because if trailers exists but if None, it'll be None.

roganjosh Over a year ago

I don't know what you mean

minboost Over a year ago

@roganjosh if the payload contained {'trailers': None} your way would set it at None instead of an empty list.

roganjosh Over a year ago

What? Have you tested your code vs mine? You're still relying on falsey.

|

Rishabh · Accepted Answer · 2018-12-27 22:45:23Z

1

You can user get method in the Python dictionary as

val = i.get('trailers', None)

This will return i['trailers'] if it exists else it will return None.

You can use this in the if condition.

answered Dec 27, 2018 at 22:45

Rishabh

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2 Comments

roganjosh Over a year ago

The None is pointless, that's the default value returned on a failed lookup. You only need the second argument if you want to override the default.

Rishabh Over a year ago

Yea, you are right. You can use it without None as well.

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