Pandas series pad function not working with apply in pandas - pandas

Question

I am trying to write the code to pad columns of my pandas dataframe with different characters. I tried to use apply function to fill '0' with zfill and it works.
print(df["Date"].apply(lambda x: x.zfill(10)))
But when I try to use pad function using apply method to my dataframe I face error:
AttributeError: 'str' object has no attribute 'pad'
The code I am trying is:
print(df["Date"].apply(lambda x: x.pad(10, side="left", fillchar="0")))
Both the zfill and pad functions are a part of pandas.Series.str. I am confused why pad is not working and zfill works. How can I achieve this functionality?
Full code:
import pandas as pd
from io import StringIO
StringData = StringIO(
"""Date,Time
パンダ,パンダ
パンダサンＤＡ１２－３,パンダーサンＤＡ１２－３
ﾊﾟﾝﾀﾞｻﾝDA12-3,ﾊﾟﾝﾀﾞｻﾝDA12-3
"""
)
df = pd.read_csv(StringData, sep=",")
print(df["Date"].apply(lambda x: x.zfill(10))) -- works
print(df["Date"].apply(lambda x: x.pad(10, side="left", fillchar="0"))) -- doesn't work
I am using pandas 1.5.1.

Answer 1

You should just not use apply, doing so you don't benefit from Series methods, but rather use pure python str methods:
print(df["Date"].str.zfill(10))
print(df["Date"].str.pad(10, side="left", fillchar="0"))
output:
0 0000000パンダ
1 パンダサンＤＡ１２－３
2 ﾊﾟﾝﾀﾞｻﾝDA12-3
Name: Date, dtype: object
0 0000000パンダ
1 パンダサンＤＡ１２－３
2 ﾊﾟﾝﾀﾞｻﾝDA12-3
Name: Date, dtype: object
multiple columns:
Now, you need to use apply, but this is DataFrame.apply, not Series.apply:
df[['col1', 'col2', 'col3']].apply(lambda s: s.str.pad(10, side="left", fillchar="0"))