pandas sort column values

Question

ie)

for the group i tried pd.groupby(b,by=[b.index.month,b.index.year])

but there was object has no attribute 'month' error

Are those actual date objects or strings?

piRSquared
– piRSquared

2017-04-18 18:49:58 +00:00
Commented Apr 18, 2017 at 18:49 — piRSquared
– piRSquared, Commented Apr 18, 2017 at 18:49
date is coloumn in dataframe objects

d.doo
– d.doo

2017-04-18 18:56:56 +00:00
Commented Apr 18, 2017 at 18:56 — d.doo
– d.doo, Commented Apr 18, 2017 at 18:56

piRSquared · Accepted Answer · 2017-04-18 19:37:58Z

1

Apply sorted with the key parameter set to pd.to_datetime

df.assign(date=df.date.apply(sorted, key=pd.to_datetime))

  id                                  date
0  a              [2015-02-01, 2015-03-01]
1  b                          [2015-03-01]
2  s              [2015-01-01, 2015-03-01]
3  f  [2015-01-01, 2015-01-01, 2015-03-01]

Then use pd.value_counts

pd.value_counts(pd.to_datetime(df.date.sum()).strftime('%Y-%m'))

2015-03    4
2015-01    3
2015-02    1
dtype: int64

debugging

You should be able to copy and paste this code... please verify that it runs as expected.

import pandas as pd

df = pd.DataFrame(dict(
        id=list('absf'),
        date=[
            ['2015-03-01', '2015-02-01'],
            ['2015-03-01'],
            ['2015-01-01', '2015-03-01'],
            ['2015-01-01', '2015-01-01', '2015-03-01']
        ]
    ))[['id', 'date']]

print(df.assign(date=df.date.apply(sorted, key=pd.to_datetime)))
print()
print(pd.value_counts(pd.to_datetime(df.date.sum()).strftime('%Y-%m')))

You should expect to see

  id                                  date
0  a              [2015-02-01, 2015-03-01]
1  b                          [2015-03-01]
2  s              [2015-01-01, 2015-03-01]
3  f  [2015-01-01, 2015-01-01, 2015-03-01]

2015-03    4
2015-01    3
2015-02    1
dtype: int64

edited Apr 18, 2017 at 19:37

answered Apr 18, 2017 at 19:01

piRSquared

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5 Comments

piRSquared Over a year ago

I don't understand what the problem is? You showed a dataframe df. Did you run this code on df? You also did not give enough information to tell what is going on.

piRSquared Over a year ago

@d.doo see the debugging section of my updated answer.

d.doo Over a year ago

df.assign(dt=df.dt.apply(sorted, key=pd.to_datetime)) there was TypeError: Unrecognized value type: <class 'str'> and ValueError: Given date string not likely a datetime.

piRSquared Over a year ago

Can you edit your question with the full stack trace?

Simon Over a year ago

Debugging code works ok for me pd.__version__ 0.19.2 - d.doo could you just confirm if the debugging code works correctly please. The problem may be with your source data. pd.to_datetime also has errors='coerce' and errors='ignore' that you could try.

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