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str3 = "HarryPotter
str3[4] # extract index 4 = "y"
str3[-1] # extract last index = "r"
str3[3,6] # starts at index 3 and extract 6 characters
str3[3..6] # from index 3 to index 6 = "ryPo"
str3[3...6] # from index 3 to index 5 = "ryP"