Join two columns:

import datetime
import pandas as pd

todays_date = datetime.datetime.now().date()
index = pd.date_range(todays_date, periods=10, freq='D')

columns = ['A', 'B', 'C']

df = pd.DataFrame(index=index, columns=columns)
df = df.fillna(0)

print(df)

C:\pandas>python example42.py
            A  B  C
2018-09-30  0  0  0
2018-10-01  0  0  0
2018-10-02  0  0  0
2018-10-03  0  0  0
2018-10-04  0  0  0
2018-10-05  0  0  0
2018-10-06  0  0  0
2018-10-07  0  0  0
2018-10-08  0  0  0
2018-10-09  0  0  0
 
C:\pandas>