How to adapt a line of code from C# to Python?

Question

Python

How to adapt this line of code

num4 = (int)Math.Round(unchecked(Conversions.ToDouble(Conversion.Oct(Strings.Asc(Conversions.ToString(num4))) + Conversion.Oct(Strings.Asc(@string))) + 666.0));

Under python?
Tried like this

num4 = int(round(float(oct(ord(str(num4))) + oct(ord(string))) + 666.0))

But it gives an error
ValueError: could not convert string to float: '0o600o164'