python – Backup of a data frame in .csv format with a different file name

For example, I import a csv file as a data frame and work on some processes on pandas

df = pd.read_csv('./label/101_5603_2019-05-02~2019-05-18.csv')
rest of codes to work on the data

How to save the result to a new csv file with the names, including the first character of the original csv files (101_5603.csv)? Thank you!