如何迭代地将结果存储在数据框中？

Question

我要检索数据框中某个日期的最大文章数。

目前，我一天只能获得20个标题。我认为这是极限。我将字体和标题放在该列中并指出日期。

import requests

url = ('https://newsapi.org/v2/everything?'
       'language=en&'
       'from=2018-12-07&'
       'to=2018-12-07&'
       'sources=financial-times,australian-financial-review,reuters,the-times-of-india&'
       'apiKey=de9e19b7547e44c4983ad761c104278f')

response = requests.get(url)

import pandas as pd
from pandas.io.json import json_normalize

# using the pandas.io.json.json_normalize() function; 
# it can produce a dataframe for you from list-and-dictionaries structure typically loaded from a JSON source.
df = json_normalize(response.json(), 'articles')

# make the datetime column a native type, and add a date-only column
df['publishedAt'] = pd.to_datetime(df['publishedAt'])
df['date'] = df['publishedAt'].dt.date

# move source dictionary into separate columns rather than dictionaries
source_columns = df['source'].apply(pd.Series).add_prefix('source_')
df = pd.concat([df.drop(['source'], axis=1), source_columns], axis=1)

Y obtengo con：

>>> pd.pivot_table(
...     df, index='date', columns='source_name', values='title',
...     aggfunc=list
... )

source_name Financial Times Reuters The Times of India
date            
2018-12-07  [Pound exodus: Brexit drives away US and Asia ...   [U.S. accuses Huawei CFO of Iran sanctions cov...   [Live 1st Test India vs Australia: Rain delays...

¿Cómoobtener 20 resultados de estas fuentes indexadas cadadía？ ¿Cómollamar a la url cada dias y almacenar sus resultados en un marco de datos de forma recursiva？

Es decir，格式为：

            articles
2007-01-01  What Sticks from '06. Somalia Orders Islamist...
2007-01-02  Heart Health: Vitamin Does Not Prevent Death ...
2007-01-03  Google Answer to Filling Jobs Is an Algorithm...
2007-01-04  Helping Make the Shift From Combat to Commerc...
2007-01-05  Rise in Ethanol Raises Concerns About Corn as...

我的尝试

dates = np.arange(np.datetime64('2018-12-09'), np.datetime64('2019-01-09'))

d = {'date'}
df = pd.DataFrame(index=d)

for date in dates:
    url = ('https://newsapi.org/v2/everything?'
       'language=en&'
       'from=%s&'
       'to=%s&'
       'sources=financial-times,australian-financial-review,reuters,the-times-of-india&'
       'apiKey=de9e19b7547e44c4983ad761c104278f')% (date,date)

    response = requests.get(url)
    # using the pandas.io.json.json_normalize() function; 
    # it can produce a dataframe for you from list-and-dictionaries structure typically loaded from a JSON source.
    df_new = json_normalize(response.json(), 'articles')

    # make the datetime column a native type, and add a date-only column
    df_new['publishedAt'] = pd.to_datetime(df_new['publishedAt'])
    df_new['date'] = df_new['publishedAt'].dt.date

    # move source dictionary into separate columns rather than dictionaries
    source_columns = df_new['source'].apply(pd.Series).add_prefix('source_')
    df_new = pd.concat([df_new.drop(['source'], axis=1), source_columns], axis=1)
    df_new = pd.pivot_table(df_new, index='date', columns='source_name', values='title',aggfunc=list)
    # to add it to the dataframe
    df.append(df_new, ignore_index=True)

但是我得到df：

date

仅此而已。就像如果什么都没发生