Pandas: How to sort dataframe rows by date of one column

Question

So I have two different data-frame and I concatenated both. All columns are the same; however, the date column has all sorts of different dates in the M/D/YR format.

dataframe dates get shuffled around later in the sequence

Is there a way to keep the whole dataframe itself and just sort the rows based on the dates in the date column. I also want to keep the format that date is in.

so basically

date        people
6/8/2015    1
7/10/2018   2
6/5/2015    0

gets converted into:

date          people
6/5/2015      0
6/8/2015      1
7/10/2018     2

Thank you!

PS: I've tried the options in the other post on this but it does not work

mad_ · Accepted Answer · 2018-07-10 19:58:59Z

4

Trying to elaborate on what can be done: Intialize/ Merge the dataframe and convert the column into datetime type

df= pd.DataFrame({'people':[1,2,0],'date': ['6/8/2015','7/10/2018','6/5/2015',]})
df.date=pd.to_datetime(df.date,format="%m/%d/%Y")
print(df)

Output:

   date      people
0   2015-06-08  1
1   2018-07-10  2
2   2015-06-05  0

Sort on the basis of date

df=df.sort_values('date')
print(df)

Output:

    date    people
2   2015-06-05  0
0   2015-06-08  1
1   2018-07-10  2

Maintain the format again:

df['date']=df['date'].dt.strftime('%m/%d/%Y')
print(df)

Output:

    date    people
2   06/05/2015  0
0   06/08/2015  1
1   07/10/2018  2

edited Jul 10, 2018 at 19:58

answered Jul 10, 2018 at 18:22

mad_

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1 Comment

ALollz Over a year ago

Since that winds up adding some leading '0's to the date, you could instead create a dummy_date column which is datetime, sort by that and then drop it to leave date truly untouched. But same basic idea :D

Jobolika · Accepted Answer · 2018-07-11 04:41:24Z

1

Try changing the 'date' column to pandas Datetime and then sort

import pandas as pd
df= pd.DataFrame({'people':[1,1,1,2],'date': 
['4/12/1961','5/5/1961','7/21/1961','8/6/1961']})
df['date'] =pd.to_datetime(df.date)
df.sort_values(by='date')

Output:

date       people

1961-04-12  1

1961-05-05  1

1961-07-21  1

1961-08-06  2

To get back the initial format:

df['date']=df['date'].dt.strftime('%m/%d/%y')

Output:

date    people
04/12/61    1

05/05/61    1

07/21/61    1

08/06/61    2

edited Jul 11, 2018 at 4:41

answered Jul 10, 2018 at 18:25

Jobolika

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1 Comment

Jobolika Over a year ago

Thank you .I added one more line of code to get the initial format and also printed the output

Alg_D · Accepted Answer · 2018-07-10 18:48:01Z

-3

why not simply?

dataset[SortBy["date"]]

can you provide what you tried or how is your structure?

In case you need to sort in reversed order do:

dataset[SortBy["date"]][Reverse]

edited Jul 10, 2018 at 18:48

answered Jul 10, 2018 at 18:08

Alg_D

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1 Comment

rafaelc Over a year ago

What is SortBy ? Where is it defined? and Reverse ? How come this answer has 3 upvotes?

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