How to encode list of numbers as base64

Question

I have a list containing negative numbers, and want to encode the list with base64. How can I do that?

I tried:

l = [-10, -48, 100, -20]
bytes(l)

But I get the error:

ValueError: bytes must be in range(0, 256)

I expect the same output as my Java code:

byte[] bytes = {-10, -48, 100, -20};
String result = Base64Utils.encodeToUrlSafeString(bytes);
System.out.println(result); // 9tBk7A==

Answer 1

The error arises because Python expects unsigned 8-bit data, which can be obtained with the modulo % operation unsigned == signed % 2 ** num_bits :

import base64

l = [-10, -48, 100, -20]
# 2 ** 8 == 256
base64.b64encode(bytes(x % 256 for x in l))
# b'9tBk7A=='