如何在Python中将日期时间转换为字符串？

我想用这段代码制作折线图：

df = pd.DataFrame.from_dict({ 'sentencess' : sentencess, 'publishedAts' : publishedAts, 'hasil_sentimens' : hasil_sentimens })
df.to_csv('chart.csv')

df['publishedAts'] = pd.to_datetime(df['publishedAts'], errors='coerce')

by_day_sentiment = df.groupby([pd.Grouper(key='publishedAts',freq='D'),'hasil_sentimens']).size().unstack('hasil_sentimens')

sentiment_dict = by_day_sentiment.to_dict('dict')

情感字典的输出是

{'Negatif ': {Timestamp('2019-08-26 00:00:00', freq='D'): 2.0, Timestamp('2019-08-27 00:00:00', freq='D'): 4.0, Timestamp('2019-08-28 00:00:00', freq='D'): 2.0, Timestamp('2019-08-29 00:00:00', freq='D'): 3.0}, 'Netral ': {Timestamp('2019-08-26 00:00:00', freq='D'): 1.0, Timestamp('2019-08-27 00:00:00', freq='D'): 3.0, Timestamp('2019-08-28 00:00:00', freq='D'): 1.0, Timestamp('2019-08-29 00:00:00', freq='D'): 3.0}, 'Positif ': {Timestamp('2019-08-26 00:00:00', freq='D'): nan, Timestamp('2019-08-27 00:00:00', freq='D'): nan, Timestamp('2019-08-28 00:00:00', freq='D'): nan, Timestamp('2019-08-29 00:00:00', freq='D'): 1.0}}

从该情感字典中，如何创建一个新的字典，但将键（现在是日期时间）更改为字符串？

Use strftime('%Y-%m-%d %H:%M:%S')

Ex:

from pandas import Timestamp
from numpy import nan
data = {'Negatif ': {Timestamp('2019-08-26 00:00:00', freq='D'): 2.0, Timestamp('2019-08-27 00:00:00', freq='D'): 4.0, Timestamp('2019-08-28 00:00:00', freq='D'): 2.0, Timestamp('2019-08-29 00:00:00', freq='D'): 3.0}, 'Netral ': {Timestamp('2019-08-26 00:00:00', freq='D'): 1.0, Timestamp('2019-08-27 00:00:00', freq='D'): 3.0, Timestamp('2019-08-28 00:00:00', freq='D'): 1.0, Timestamp('2019-08-29 00:00:00', freq='D'): 3.0}, 'Positif ': {Timestamp('2019-08-26 00:00:00', freq='D'): nan, Timestamp('2019-08-27 00:00:00', freq='D'): nan, Timestamp('2019-08-28 00:00:00', freq='D'): nan, Timestamp('2019-08-29 00:00:00', freq='D'): 1.0}}

print({k: {m.strftime('%Y-%m-%d %H:%M:%S'): v for m, v in v.items()} for k, v in data.items()})

Output:

{'Negatif ': {'2019-08-26 00:00:00': 2.0,
              '2019-08-27 00:00:00': 4.0,
              '2019-08-28 00:00:00': 2.0,
              '2019-08-29 00:00:00': 3.0},
 'Netral ': {'2019-08-26 00:00:00': 1.0,
             '2019-08-27 00:00:00': 3.0,
             '2019-08-28 00:00:00': 1.0,
             '2019-08-29 00:00:00': 3.0},
 'Positif ': {'2019-08-26 00:00:00': nan,
              '2019-08-27 00:00:00': nan,
              '2019-08-28 00:00:00': nan,
              '2019-08-29 00:00:00': 1.0}}