Now, we are redefining max, so up to this line, max used to be a function, but after line 4 is executed max is set to an integer, that is the largest number in this list.
According to Pythagoras Theorem, the diagonal length would be square root of two; but try as he might, Hippasus could not express this as a ratio of two integers.
So int is short for integer and that represents a whole number and str is short for string, so here we're subtracting a string from an integer, and Python doesn't know what to do with it.
So, you have learned that in Python programming language you have 2 types of numbers, integers which are whole numbers like 10, they don't have a decimal point, and floating point numbers or floats.