Pygal bar chart says “No data”

Question

I am trying to create a bar graph in pygal that uses the api for hacker news and charts the most active news based on comments. I posted my code below, but I cannot figure out why my graph keep saying "No data"??? Any suggestions? Thanks!

import requests
import pygal

from pygal.style import LightColorizedStyle as LCS, LightenStyle as LS

from operator import itemgetter

# Make an API call, and store the response.
url = 'https://hacker-news.firebaseio.com/v0/topstories.json'
r = requests.get(url)
print("Status code:", r.status_code)

# Process information about each submission.
submission_ids = r.json()
submission_dicts = []
for submission_id in submission_ids[:30]:
    # Make a separate API call for each submission.
    url = ('https://hacker-news.firebaseio.com/v0/item/' +
           str(submission_id) + '.json')
    submission_r = requests.get(url)
    print(submission_r.status_code)
    response_dict = submission_r.json()

    submission_dict = {
        'comments': int(response_dict.get('descendants', 0)),
        'title': response_dict['title'],
        'link': 'http://news.ycombinator.com/item?id=' + str(submission_id),
    }
    submission_dicts.append(submission_dict)

# Visualization
my_style = LS('#336699', base_style=LCS)

my_config = pygal.Config()
my_config.show_legend = False
my_config.title_font_size = 24
my_config.label_font_size = 14
my_config.major_label_font_size = 18
my_config.show_y_guides = False
my_config.width = 1000

chart = pygal.Bar(my_config, style=my_style)
chart.title = 'Most Active News on Hacker News'

chart.add('', submission_dicts)
chart.render_to_file('hn_submissons_repos.svg')

Answer 1

The values in the array passed to the add function need to be either numbers or dicts that contain the key value (or a mixture of the two). The simplest solution would be to change the keys used when creating submission_dict:

submission_dict = {
    'value': int(response_dict.get('descendants', 0)),
    'label': response_dict['title'],
    'xlink': 'http://news.ycombinator.com/item?id=' + str(submission_id),
}

Notice that link has become xlink, this is one of the optional parameters that are defined in the Value Configuration section of the pygal docs.