Create a last day of month indicator in python

Question

How can I create an indicator for last day of the month?

Please help I've been struggling on this.

Input

Dates            Item        Sales           
2017-01-01       Apple       10
2017-01-02       Pear        10 
2017-01-31       Apple       10
2017-02-02       Apple       10
2017-01-28       Apple       10

Output

Dates            Item        Sales      Last day of month      
2017-01-01       Apple       10         No    
2017-01-02       Pear        10         No
2017-01-31       Apple       10         Yes
2017-02-02       Apple       10         No
2017-02-28       Apple       10         Yes

Possible duplicate of [Get Last Day of the Month in Python](https://stackoverflow.com/questions/42950/get-last-day-of-the-month-in-python) — Patrick Artner, Nov 18 '17 at 18:22

jezrael · Accepted Answer · 2017-11-18T18:45:40.337

4

Use numpy.where with dt.is_month_end:

df['Last day of month'] = np.where(df['Dates'].dt.is_month_end, 'Yes', 'No')
print (df)
       Dates   Item  Sales Last day of month
0 2017-01-01  Apple     10                No
1 2017-01-02   Pear     10                No
2 2017-01-31  Apple     10               Yes
3 2017-02-02  Apple     10                No
4 2017-02-28  Apple     10               Yes

Thanks, Anton vBR for solution inspired by Wen:

df['Dates'].dt.is_month_end.map({1:'Yes',0:'No'})

edited Nov 18 '17 at 18:45

answered Nov 18 '17 at 18:21

jezrael

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Obviously the right choice if pd already has a function for it. +1. Inspired by @Wen I think: `df['Dates'].dt.is_month_end.map({1:'Yes',0:'No'})` is easier to read. – Anton vBR Nov 18 '17 at 18:42

score 2 · Answer 2 · answered Nov 18 '17 at 18:37

2

By using pd.offsets

df['Last day of month']=(df.Dates==df.Dates+pd.offsets.MonthEnd(0)).map({1:'Yes',0:'No'})
df
Out[275]: 
       Dates   Item  Sales Last day of month
0 2017-01-01  Apple     10                No
1 2017-01-02   Pear     10                No
2 2017-01-31  Apple     10               Yes
3 2017-02-02  Apple     10                No
4 2017-02-28  Apple     10               Yes

answered Nov 18 '17 at 18:37

BENY

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1

Nice, was about to post something very similar. I liked the map dict to convert True False. – Anton vBR Nov 18 '17 at 18:41

Create a last day of month indicator in python

2 Answers2