Question

I’m using sqlalchemy-flask for my projects as well as json module.

I have two classes I’m pulling data from.

The two data types are Ints and List (I made sure of this by using type). When I try to append the int to the list I get None. Whats wrong?

def update_retweet_count(TWEET, TWEET_has_retweet):

    if type(json.loads(TWEET_has_retweet.js_rt)) != list:
        list_of_retweets = list([0])
    else:
        list_of_retweets = list(json.loads(TWEET_has_retweet.js_rt))

    new_rtc = int(TWEET.tmp_rt_count)

    x = list_of_retweets.append(new_rtc)
    print x 

When I run above X is None.

4 Hours later I try this below and It works!

def update_retweet_count(TWEET, TWEET_has_retweet):
    if type(json.loads(TWEET_has_retweet.js_rt)) != list:
        list_of_retweets = list([0])
    else:
        list_of_retweets = list(json.loads(TWEET_has_retweet.js_rt))

    lst =[]

    new_rtc = int(TWEET.tmp_rt_count)

    [lst.append(y) for y in list_of_retweets]

    lst.append(new_rtc)

    print lst

Why does the first code not work?

Thank you!

Fernando

Answer 1

list.append always returns None: it changes the list in place. You do:

x = list_of_retweets.append(new_rtc)
print x

in the first example and:

lst.append(new_rtc)
print lst

in the second (correct) example.