使用Python在Pandas数据框中创建星期几列

Question

使用Python在Pandas数据框中创建星期几列

我想将csv文件读入pandas数据帧,将一列日期从字符串格式解析为日期对象,然后生成一个新列,指示星期几.

这就是我正在尝试的:

我想做的是:

import pandas as pd

import csv

df = pd.read_csv('data.csv', parse_dates=['date']))

df['day-of-week'] = df['date'].weekday()


AttributeError: 'Series' object has no attribute 'weekday'

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谢谢您的帮助.詹姆士

Answer 1

熊猫0.23+

使用pandas.Series.dt.day_name(),因为pandas.Timestamp.weekday_name已被弃用:

import pandas as pd


df = pd.DataFrame({'my_dates':['2015-01-01','2015-01-02','2015-01-03'],'myvals':[1,2,3]})
df['my_dates'] = pd.to_datetime(df['my_dates'])

df['day_of_week'] = df['my_dates'].dt.day_name()

输出:

    my_dates  myvals day_of_week
0 2015-01-01       1    Thursday
1 2015-01-02       2      Friday
2 2015-01-03       3    Saturday

熊猫0.18.1+

正如用户jezrael在下面指出的那样,dt.weekday_name在0.18.1 Pandas Docs版本中添加了

import pandas as pd

df = pd.DataFrame({'my_dates':['2015-01-01','2015-01-02','2015-01-03'],'myvals':[1,2,3]})
df['my_dates'] = pd.to_datetime(df['my_dates'])
df['day_of_week'] = df['my_dates'].dt.weekday_name

输出:

    my_dates  myvals day_of_week
0 2015-01-01       1    Thursday
1 2015-01-02       2      Friday
2 2015-01-03       3    Saturday

原答案:

用这个:

http://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.dt.dayofweek.html

看到这个:

获取DataFrame的Datetime列的工作日/星期几

如果你想要一个字符串而不是一个整数做这样的事情:

import pandas as pd

df = pd.DataFrame({'my_dates':['2015-01-01','2015-01-02','2015-01-03'],'myvals':[1,2,3]})
df['my_dates'] = pd.to_datetime(df['my_dates'])
df['day_of_week'] = df['my_dates'].dt.dayofweek

days = {0:'Mon',1:'Tues',2:'Weds',3:'Thurs',4:'Fri',5:'Sat',6:'Sun'}

df['day_of_week'] = df['day_of_week'].apply(lambda x: days[x])

输出:

    my_dates  myvals day_of_week
0 2015-01-01       1       Thurs
1 2015-01-02       2         Fri
2 2015-01-01       3       Thurs

Answer 2

在版本0.18.1中添加dt.weekday_name:

print df
    my_dates  myvals
0 2015-01-01       1
1 2015-01-02       2
2 2015-01-03       3

print df.dtypes
my_dates    datetime64[ns]
myvals               int64
dtype: object

df['day_of_week'] = df['my_dates'].dt.weekday_name
print df
    my_dates  myvals day_of_week
0 2015-01-01       1    Thursday
1 2015-01-02       2      Friday
2 2015-01-03       3    Saturday

另一个解决方案assign:

print df.assign(day_of_week = df['my_dates'].dt.weekday_name)
    my_dates  myvals day_of_week
0 2015-01-01       1    Thursday
1 2015-01-02       2      Friday
2 2015-01-03       3    Saturday

Answer 3

使用dt.weekday_name是因为过时pandas 0.23.0，相反，使用dt.day_name()：

df = pd.DataFrame({'my_dates':['2015-01-01','2015-01-02','2015-01-03'],'myvals':[1,2,3]})
df['my_dates'] = pd.to_datetime(df['my_dates'])

df['my_dates'].dt.day_name()

0    Thursday
1      Friday
2    Saturday
Name: my_dates, dtype: object

Answer 4

df =df['Date'].dt.dayofweek

dayofweek 是数字格式

Answer 5

以防万一 .dt 不适合您。尝试 .DatetimeIndex 可能会有所帮助。希望这里的代码和我们的测试结果可以帮助您解决这个问题。问候，

import pandas as pd
import datetime

df = pd.DataFrame({'Date':['2015-01-01','2015-01-02','2015-01-03'],'Number':[1,2,3]})

df['Day'] = pd.DatetimeIndex(df['Date']).day_name() # week day name
df.head()