Question

I’m trying to perform the modulus of a value in python, but I’m getting errors as it’s interpretting the modulus as a string formatting constant, from my knowledge. My initial guess would be to type cast this, but then it hangs.

    val = pow(a,n,p)
    val = y1*val
    val = val % p

Are the two lines of code corresponding to this question. Right now, when I run this, I get:
TypeError: not all arguments converted during string formatting
At the second line.

If I wrap val into an integer and type cast it…it takes extremely long to calculate.

I’m not too skilled with python, my guess is I’m missing something simple, but what?

Answer 1

If yu are getting this error, y1 itself is a string. You can’t perform numeric calculations with strings – when you do “int(y1) ” – it is not casting, it is converting the number represented by characters inside the string o an actual numeric value – and that is the only way you can perform numeric operations on it.

If it is takin thta log, it is probable because you are trying convert “y1 * val” to int – which is wrong already – if y1 is a string, “y1 * val” gives you y1 concatenated to itself “val” times – so it would be a really huge number. You need to have the value i n “y1” as a number before multiplying – as in:

val  = int(y1) * val