Json dictionnary on Redis - Printable Version

Json dictionnary on Redis - Printable Version

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Json dictionnary on Redis - katsu707 - Dec-04-2018

Hi everyone, I'm a complete beginner and here's my issue:

I have Flask as a webserver, Redis is counting the number of hits on the root. I added a arg "name".
I want to store and return a different count that I wish to link to the "name" var.
I got some help and they advised to use a JSON dictionnary. I'm struggling with the implementation. My code looks like this:

from flask import Flask
from redis import Redis
import json

app = Flask(__name__)
redis = Redis(host='redis', port=6379)

@app.route('/')
@app.route('/<name>')
def hello(name):
    counts = json.loads(redis.get('hits'),('{}'))
    try:
         counts[name] += 1
    except KeyError:
         counts[name] = 1
    redis.set('hits', json.dumps(counts))
    return 'Hello {} I have been seen {} times.\n'.format(name,counts[name])

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=8000, debug=True)

I keep getting this error and I don't know why...

Error: File "/app/app3.py", line 11, in hello
    counts = json.loads(redis.get('hits'),('{}'))
TypeError: loads() takes 1 positional argument but 2 were given

Thanks a lot!
K.

RE: Json dictionnary on Redis - DeaD_EyE - Dec-04-2018

The function json.loads takes 1 positional argument but 2 were given.
The error message is very helpful.

In line number 13, you should change the code from:

counts = json.loads(redis.get('hits'),('{}'))

counts = json.loads(redis.get('hits'))

When your intention was to have a default argument, if the key does not exist in redis (returns None), you can use following trick:

counts = json.loads(redis.get('hits')) or {'hits': 0, 'something-else': 'foo'}

First the key 'hits' is returned by redis. If this key is None the dict on the right side is assigned to the name counts. The first object, which evaluates to True is taken.

0, 0.0, (0.0+0j), False, None, empty: bytes, bytearray, list, tuple, dict, set evaluates to False.

bool(None) == False
bool({}) == False
bool([]) == False

You can use this knowledge for default values:

def hello(greeting=''):
    '''
    print greeting on the screen
    if greeting is empty, Hello World is printed
    '''
    text = greeting or 'Hello World'
    print(text)