How to convert string of 1s and 0s into binary to be added? [duplicate]

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• Converting string of 1s and 0s into binary value 5 answers

I am reading a .txt file into a large string and splitting it up to add certain parts of the string. So I have 2 strings, rt and rd, that are 2 bits long, "01", "11". How do I convert them into binary and add them together?