获取DataFrame的Datetime列的工作日/星期几 [英] Get weekday/day-of-week for Datetime column of DataFrame

问题描述

我有一个类似于以下内容的DataFrame df(摘录，"Timestamp"是索引):

I have a DataFrame df like the following (excerpt, 'Timestamp' are the index):

Timestamp              Value
2012-06-01 00:00:00     100
2012-06-01 00:15:00     150
2012-06-01 00:30:00     120
2012-06-01 01:00:00     220
2012-06-01 01:15:00      80
...and so on.

我需要一个新列df['weekday']，其中包含相应的时间戳记的星期几/星期几.

I need a new column df['weekday'] with the respective weekday/day-of-week of the timestamps.

我怎么能得到这个?

推荐答案

使用新的

Use the new dt.dayofweek property:

In [2]:

df['weekday'] = df['Timestamp'].dt.dayofweek
df
Out[2]:
            Timestamp  Value  weekday
0 2012-06-01 00:00:00    100        4
1 2012-06-01 00:15:00    150        4
2 2012-06-01 00:30:00    120        4
3 2012-06-01 01:00:00    220        4
4 2012-06-01 01:15:00     80        4

在Timestamp是您的索引的情况下，您需要重置索引，然后调用dt.dayofweek属性:

In the situation where the Timestamp is your index you need to reset the index and then call the dt.dayofweek property:

In [14]:

df = df.reset_index()
df['weekday'] = df['Timestamp'].dt.dayofweek
df
Out[14]:
            Timestamp  Value  weekday
0 2012-06-01 00:00:00    100        4
1 2012-06-01 00:15:00    150        4
2 2012-06-01 00:30:00    120        4
3 2012-06-01 01:00:00    220        4
4 2012-06-01 01:15:00     80        4

奇怪的是，如果您尝试从索引创建一个序列以不重置索引，您将获得NaN值，就像使用reset_index的结果来调用dt.dayofweek属性而不分配返回原始df:

Strangely if you try to create a series from the index in order to not reset the index you get NaN values as does using the result of reset_index to call the dt.dayofweek property without assigning the result of reset_index back to the original df:

In [16]:

df['weekday'] = pd.Series(df.index).dt.dayofweek
df
Out[16]:
                     Value  weekday
Timestamp                          
2012-06-01 00:00:00    100      NaN
2012-06-01 00:15:00    150      NaN
2012-06-01 00:30:00    120      NaN
2012-06-01 01:00:00    220      NaN
2012-06-01 01:15:00     80      NaN
In [17]:

df['weekday'] = df.reset_index()['Timestamp'].dt.dayofweek
df
Out[17]:
                     Value  weekday
Timestamp                          
2012-06-01 00:00:00    100      NaN
2012-06-01 00:15:00    150      NaN
2012-06-01 00:30:00    120      NaN
2012-06-01 01:00:00    220      NaN
2012-06-01 01:15:00     80      NaN

编辑

正如@joris用户向我指出的那样，您可以只访问索引的weekday属性，因此以下内容将有效并且更加紧凑:

As pointed out to me by user @joris you can just access the weekday attribute of the index so the following will work and is more compact:

df['Weekday'] = df.index.weekday

这篇关于获取DataFrame的Datetime列的工作日/星期几的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！