2.51 * 100 = 250.999999999997
The int() function simply truncates the number at the decimal point, giving 250. Use
int(round(2.51*100))
to get 251 as an integer. In general, floating point numbers cannot be represented exactly. One should therefore be careful of round-off errors. As mentioned, this is not a Python-specific problem. It’s a recurring problem in all computer languages.