convert batch code to python script

Hi I want to convert windows batch file into linux python script. I can able to write python script but I am unable to understand some code of window batch file which I need to convert into linux python script

:vars

:: Main folder
set BASE_DIR=%~dp0

:: Downloadable data 
set DATA_DIR=%BASE_DIR%\data.downloadable
set              "DBF_DIR=%data_dir%\101\dbf"
set       "CSV_DIR_UPDATE=%data_dir%\101\csv.update"
set "CSV_DIR_FULL_ARCHIVE=%data_dir%\101\csv.full"
set              "SQL_DIR=%data_dir%\101\sql"
set              "RAR_DIR=%data_dir%\101\rarzip"

:: Private data 
set "DATA_DIR_PRIVATE=%BASE_DIR%\data.private"
set     "FORM_DIR_VEB=%data_dir_private%\veb\form"
set      "CSV_DIR_VEB=%data_dir_private%\veb\csv"

:: Output
set "DIR_OUTPUT=%BASE_DIR%\output"


 ::::::::::::::::::::::::::::::::::::::::
 :    add some paths
 PATH %PATH%;%BASE_DIR%
 PATH %PATH%;%BASE_DIR%\task\maintain
 PATH %PATH%;%BASE_DIR%\py

::::::::::::::::::::::::::::::::::::::::

if not exist %DATA_DIR%              md %DATA_DIR%
if not exist %DBF_DIR%               md %DBF_DIR%
if not exist %CSV_DIR_UPDATE%        md %CSV_DIR_UPDATE%
if not exist %CSV_DIR_FULL_ARCHIVE%  md %CSV_DIR_FULL_ARCHIVE%
if not exist %RAR_DIR%               md %RAR_DIR% 
if not exist %SQL_DIR%               md %SQL_DIR% 
if not exist %DIR_OUTPUT%            md %DIR_OUTPUT% 

echo Directories checked or created...

:end

::::::::::::::::::::::::::::::::::::::::

can you please explain what above code do exactly, atleast give me logic so that I can implement in python script