what does rstrip mean in python code example

Example 1: what is r strip function in python

#!/usr/bin/python

str = "     this is string example....wow!!!     ";
print str.rstrip()
str = "88888888this is string example....wow!!!8888888";
print str.rstrip('8')

#the answer

#this is string example....wow!!!
#88888888this is string example....wow!!!

Example 2: rstrip python3

#python3 program of rstrip method with optional argument
s = "Hello There     "
a = "s"
print(s.rstrip()) # prints s without any spaces at the end
print(s.rstrip(a)) # prints s without any characters of value a at the end