Remove an element from string if it appears twice

Question

I want to remove an element from a string if it appears twice, for example :
str1 = "ggtggt
The output should be" gt"

Answer 1

Out of many ways one way to do it
str1 = "ggtggt"
str2=""
for i in str1:
if i not in str2:
str2+=i
print(str2)
it won't remove element but add non repeating element to new string

Answer 2

A very common way is also to use a set. A set is a data container, but does only allow unique elements. So all duplicated elements will be removed automatically when converting a string to a set:
str1 = "ggtggt"
print(''.join(set(str1)))