'pg_dump' is not recognized as an internal or external command,

I have a code which should do a backup of existing postgresql , but when i run the code am getting error

'pg_dump' is not recognized as an internal or external command,

i tried running command pg_dump in command prompt it shows error

pg_dump: error: connection to server at "localhost" (::1), port 5432 failed: FATAL: role "HP-LSC" does not exist

i kept the folder path of bin and lib in environment variable, but it is still showing the same error , Can anyone help me in this please

below is the code:

import subprocess

DB_NAME = 'postgress'  # your db name

DB_USER = 'postgres' # you db user
DB_HOST = "localhost"
DB_PASSWORD = 'abc'# your db password
dump_success = 1
print ('Backing up %s database ' % (DB_NAME))

command_for_dumping = f'pg_dump --host={DB_HOST} ' \
            f'--dbname={DB_NAME} ' \
            f'--username={DB_USER} ' \
            f'--no-password ' \
            f'--file=backup.dmp '
try:
     proc = subprocess.Popen(command_for_dumping, shell=True, env={
                   'PGPASSWORD': DB_PASSWORD
                   })
     proc.wait()

except Exception as e:
        dump_success = 0
        print('Exception happened during dump %s' %(e))


if dump_success:
    print('db dump successfull')
print(' restoring to a new database database')



backup_file = 'tmp/backup.dmp'
"""give absolute path of your dump file. This script will create the backup.dmp in the same directory from which u are running the script """

if not dump_success:
    print('dump unsucessfull. retsore not possible')
else:
    try:
        process = subprocess.Popen(
                        ['pg_restore',
                         '--no-owner',
                         '--dbname=postgresql://{}:{}@{}:{}/{}'.format('postgres',#db user
                                                                       'abc', #db password
                                                                       'localhost',  #db host
                                                                       '5432', 'ReplicaDB'), #db port ,#db name
                         '-v',
                         backup_file],
                        stdout=subprocess.PIPE
                    )
        output = process.communicate()[0]
    except Exception as e:
           print('Exception during restore %e' %(e) )

Thank you