CODEWITHSUNDEEP
pythonpandasloopsdate
Baiii
Baiii

Reputation: 99

Compare two date by month & date Python

I have two columns of dates need to be compared, date1 is a list of certain dates, date2 is random date (dob). I need to compare month and day by some conditon to make a flag. sample like:

df_sample = DataFrame({'date1':('2015-01-15','2015-01-15','2015-03-15','2015-04-15','2015-05-15'),
                       'dob':('1999-01-25','1987-12-12','1965-03-02','2000-08-02','1992-05-15')}

I create a function based on condition below

def eligible(date1,dob):
  if date1.month - dob.month==0 and date1.day <= dob.day:
    return 'Y'
  elif date1.month - dob.month==1 and date1.day > dob.day:
    return 'Y'
  else:
    return 'N'

I want to apply this function to orginal df which has more than 5M rows, hence for loop is not efficiency, is there any way to achieve this?

Datatype is date, not datetime

Upvotes: 3

Views: 6585

Answers (2)

jezrael
jezrael

Reputation: 862591

I think you need numpy.where with conditions chained by | (or):

df_sample['date1'] = pd.to_datetime(df_sample['date1'])
df_sample['dob'] = pd.to_datetime(df_sample['dob'])

months_diff = df_sample.date1.dt.month  - df_sample.dob.dt.month
days_date1 = df_sample.date1.dt.day
days_dob = df_sample.dob.dt.day

m1 = (months_diff==0) & (days_date1 <= days_dob)
m2 = (months_diff==1) & (days_date1 > days_dob)

df_sample['out'] = np.where(m1 | m2 ,'Y','N')
print (df_sample)
       date1        dob out
0 2015-01-15 1999-01-25   Y
1 2015-01-15 1987-12-12   N
2 2015-03-15 1965-03-02   N
3 2015-04-15 2000-08-02   N
4 2015-05-15 1992-05-15   Y

Upvotes: 3

DYZ
DYZ

Reputation: 57033

Using datetime is certainly beneficial:

df_sample['dob'] = pd.to_datetime(df_sample['dob'])
df_sample['date1'] = pd.to_datetime(df_sample['date1'])

Once you have it, your formula can be literally applied to all rows:

df_sample['eligible'] = 
              (  (df_sample.date1.dt.month == df_sample.dob.dt.month)\
               & (df_sample.date1.dt.day <= df_sample.dob.dt.day)) |\
              (  (df_sample.date1.dt.month - df_sample.dob.dt.month == 1)\
               & (df_sample.date1.dt.day > df_sample.dob.dt.day))

The result is boolean (True/False), but you can easily convert it to "Y"/"N", if you want.

Upvotes: 0

Related Questions