The hex() function converts a specified integer number into a hexadecimal string representation.

Use int(x, base) with 16 as base to convert the string x to an integer. Call hex(number) with the integer as number to convert it to hexadecimal.

hex_string = "0xAA"

"0x" also required

an_integer = int(hex_string, 16)

hex_value = hex(an_integer)

print(hex_value)

Output

0xaa

Your class.function expects an integer which can be represented either by a decimal or a hexadecimal literal, so that these two calls are completely equivalent:

class.function(0x77)
class.function(119)  # 0x77 == 119

Even print(0x77) will show 119 (because decimal is the default representation).

So, we should rather be talking about converting a string representation to integer. The string can be a hexadecimal representation, like '0x77', then parse it with the base parameter:

 >>> int('0x77', 16)
 119

or a decimal one, then parse it as int('119').

Still, storing integer whenever you deal with integers is better.

EDIT: as @gnibbler suggested, you can parse as int(x, 0), which handles both formats.

Try this:

hex_str = "0xAD4"
hex_int = int(hex_str, 16)
new_int = hex_int + 0x200
print hex(new_int)

If you don't like the 0x in the beginning, replace the last line with

print hex(new_int)[2:]

You can transform your string to an integer generator. Apply hexadecimal formatting for each element and intercalate with a separator:

>>> s = "Hello, World!"
>>> ":".join("{:02x}".format(ord(c)) for c in s)
'48:65:6c:6c:6f:2c:20:57:6f:72:6c:64:21