Fastest way to get specific key from a dict if it is found-CodePudding

I am currently writing a scraper that reads from an API that contains a JSON. By doing response.json() it would return a dict where we could easily use the e.g response["object"]to get the value we want as I assume that converts it to a dict. The current mock data looks like this:

data = {
    'id': 336461,
    'thumbnail': '/images/product/123456?trim&h=80',
    'variants': None,
    'name': 'Testing',
    'data': {
        'Videoutgång': {
            'Typ av gränssnitt': {
                'name': 'Typ av gränssnitt',
                'value': 'PCI Test'
            }
        }
    },
    'stock': {
        'web': 0,
        'supplier': None,
        'displayCap': '50',
        '1': 0,
        'orders': {
            'CL': {
                'ordered': -10,
                'status': 1
            }
        }
    }
}

What I am looking after is that the API sometimes does contain "orders -> CL" but sometime doesn't . That means that both happy path and unhappy path is what I am looking for which is the fastest way to get a data from a dict.

I have currently done something like this:

data = {
    'id': 336461,
    'thumbnail': '/images/product/123456?trim&h=80',
    'variants': None,
    'name': 'Testing',
    'data': {
        'Videoutgång': {
            'Typ av gränssnitt': {
                'name': 'Typ av gränssnitt',
                'value': 'PCI Test'
            }
        }
    },
    'stock': {
        'web': 0,
        'supplier': None,
        'displayCap': '50',
        '1': 0,
        'orders': {
            'CL': {
                'ordered': -10,
                'status': 1
            }
        }
    }
}

if (
        "stock" in data
        and "orders" in data["stock"]
        and "CL" in data["stock"]["orders"]
        and "status" in data["stock"]["orders"]["CL"]
        and data["stock"]["orders"]["CL"]["status"]
):
    print(f'{data["stock"]["orders"]["CL"]["status"]}: {data["stock"]["orders"]["CL"]["ordered"]}')

1: -10

However my question is that I would like to know which is the fastest way to get the data from a dict if it is in the dict?

CodePudding user response：

I got your point. For this question, since your stock has just 4 values it is hard to say if .get() method will work faster than using a loop or not. If your dictionary would have more items then certainly .get() would have worked much faster but since there are few keys, using loop will not make much difference.

CodePudding user response：

Lookups are faster in dictionaries because Python implements them using hash tables. If we explain the difference by Big O concepts, dictionaries have constant time complexity, O(1). This is another approach using .get() method as well:

data = {
    'id': 336461,
    'thumbnail': '/images/product/123456?trim&h=80',
    'variants': None,
    'name': 'Testing',
    'data': {
        'Videoutgång': {
            'Typ av gränssnitt': {
                'name': 'Typ av gränssnitt',
                'value': 'PCI Test'
            }
        }
    },
    'stock': {
        'web': 0,
        'supplier': None,
        'displayCap': '50',
        '1': 0,
        'orders': {
            'CL': {
                'ordered': -10,
                'status': 1
            }
            
        }
    }
}
if (data.get('stock', {}).get('orders', {}).get('CL')):
    print(f'{data["stock"]["orders"]["CL"]["status"]}: {data["stock"]["orders"]["CL"]["ordered"]}')

Here is a nice writeup on lookups in Python with list and dictionary as example.