Reading Files In Python

#importing the required libraries

 import pandas as pd

import shutil

from shutil import copyfile 

from datetime import date,datetime, timedelta 

import os

source_folder = r"D:\\SourceFiles\\"

dest_folder=r"D:\\DestinationFiles\\"

###Loop throught the source_folder getting the datepart from it filename and subtract 1 from it

###and then recombine the again with yesterday.

for file in os.listdir(source_folder):

    r=file.rfind("_")

    date_string=file[r:][1:9]

    fname=file[:r][:]

    remainingpart=file[r:][9:]

    date_object = datetime.strptime(date_string, "%Y%m%d")

    date_object=date_object-timedelta(days=1)

    date_object=date_object.strftime("%Y%m%d")

    #print(fname+"_"+date_object+remainingpart)

    old_file=source_folder+file

    new_file=dest_folder+fname+"_"+date_object+remainingpart

    #print("oldfile_name",old_file, "Newfile name", new_file)

    os.rename(old_file, new_file)

#############Reading the files from the dest_folder one by one and rewrite to Final folder

for file in os.listdir(dest_folder):

    print(file)

    df = pd.read_csv("D:\\DestinationFiles\\"+file, dtype=str)

    print(df)

    df.to_csv("D:\\Final\\"+file, index=False)

#####Adding Columns of SysDATE and File_Name in existing DataFrame Using Lists

####Inserting BlankColumn in Beginning of DataFrame 

import pandas

from datetime import date,datetime, timedelta

df=pandas.read_csv("1.csv")

for i in range(0,len(df)):

    date_string=df['Date'].iloc[i]

    do = datetime.strptime(date_string, '%d-%b-%y')

    SysDATE=do.strftime('%Y%m%d')

    datelist.append(SysDATE)

    filelist.append("filename_"+SysDATE)

    

df['SDATE']=datelist

df['File']=filelist

df.insert(0,'Unnamed 0',' ')