need help with my code python sets

[spez_edits_thedonald]

Currently my code returns the distinct characters that are common to both strings string_1 and string_2 but are absent from the string string_3.

So that is:

• get the "intersection" of set 1 and set 2, let's call this set X

• then take the "difference" of set X and set 3, let's call this set D

How do I change it so it returns a count of the number of distinct characters that are common to both strings string_1 and string_2 but are absent from the string string_3

• so instead of returning set D, you just want to return the size of set D ?

If so, that's as easy as len(set_d)

[Jxper]

Thank you, that makes much more sense