python pandas add leading zero to make all months 2 digits

Question

How can I add a leading zero so i have a minimum of double digits.

     Week product  quantity        Month
0  201301    coke       1.5           1
1  201302   fanta       1.7           2
2  201304    coke       3.6           5
3  201306  sprite       2.4          10
4  201308   pepsi       2.9          12

i.e convert the above dataframe to be the below:

     Week product  quantity         Month
0  201301    coke       1.5           01
1  201302   fanta       1.7           02
2  201304    coke       3.6           05
3  201306  sprite       2.4           10
4  201308   pepsi       2.9           12

Answer 1

use map() method of Series with "{:02}".format:

data = """     Week product  quantity        Month
0  201301    coke       1.5           1
1  201302   fanta       1.7           2
2  201304    coke       3.6           5
3  201306  sprite       2.4          10
4  201308   pepsi       2.9          12
"""

import pandas as pd
import io

df = pd.read_csv(io.BytesIO(data), delim_whitespace=True)
df["Month"] = df.Month.map("{:02}".format)

Answer 2

In Python 2.7 you can format this value using

>>> month = 9
>>> '{:02}'.format(month)
'09'

here 2 in {:02} specifies convert the input digit in 2 chars by prefixing '0'. If input digit is of length 2 then that digit will remain unchanged.