使用 Python 在 Panda 数据框架中创建每周一天的专栏

使用 Python 在 Panda 数据框架中创建每周一天的专栏

我希望将一个 csv 文件读入熊猫数据框，将一列日期从字符串格式解析为一个日期对象，然后生成一个指示星期几的新列。

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'

谢谢你的帮助。 詹姆斯

187020 次浏览
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最佳答案

Pandas 0.23+

Use pandas.Series.dt.day_name(), since pandas.Timestamp.weekday_name has been deprecated:

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()

Output:

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

Pandas 0.18.1+

As user jezrael points out below, dt.weekday_name was added in version 0.18.1 Pandas Docs

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

Output:

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

Original Answer:

Use this:

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

See this:

Get weekday/day-of-week for Datetime column of DataFrame

If you want a string instead of an integer do something like this:

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])

Output:

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

In version 0.18.1 is added 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

Another solution with 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
小开

Using dt.weekday_name is deprecated since pandas 0.23.0, instead, use 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
小开 
df =df['Date'].dt.dayofweek

dayofweek is in numeric format

小开

Just in case if .dt doesn't work for you. Trying .DatetimeIndex might help. Hope the code and our test result here help you fix it. Regards,

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()

enter image description here

小开

When date is the index

…and only the first three letters are required:

df['day'] = df.index.day_name().str[:3]
小开

data['Day_Of_Week'] = pd.DatetimeIndex(data['Birth_Date']).day_name()

Command appends new column/feature as data['Day_Of-Week'] from data['Birth_Date'] column which is present in dataset/csv previously.


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