An interpreter for the Quiner esolang (more info on https://esolangs.org/wiki/Quiner)

quiner interpreter.py

code = input("enter quiner code: ")
data = ""
code_ip = 0
data_ip = 0

debug = False

a = 1
a_len = 0
inputs = ""
#for i in range(30):
while True:
    if debug:
        print("---")
        print(code)
        print(data)

    if len(data) <= data_ip:
        data_ip = len(data)
    if len(code) <= code_ip:
        code_ip = len(code)
        if len(data) <= data_ip:
            break # halt if both programs are done
        else:
            # switch them around if data program is not done but code program is
            (code, data) = (data, code)
            (code_ip, data_ip) = (data_ip, code_ip)
    instruction = code[code_ip]
    if instruction in "1234567890":
        if debug:
            print("digit")
        if a_len == 0:
            a = 0
        a *= 10
        a += int(instruction)
        a_len += 1
    else:

        if debug:
            print("instruction")
            print(a)
            print(a_len)

        if instruction == "*":
            data = data[:-a]
        elif instruction == ",":
            while len(inputs) < a:
                inputs += input()
                inputs += "\n"
            data += inputs[:a]
            inputs = inputs[a:]
        elif instruction == ".":
            print(data[-a:], end="")
            data = data[:-a]
        elif instruction == ">":
            data += code[code_ip+1:code_ip+1+a]
            code_ip += a
        elif instruction == "<":
            data += code[max(0,code_ip-a_len-a):code_ip-a_len]
        elif instruction == "/":
            if code[code_ip+1] == "/":
                code_ip += a + 1
            else:
                code_ip += 1
        elif instruction == "+":
            if a_len == 0:
                a = 2
            chars = data[-a:]
            data = data[:-a]
            res = chr(sum(map(ord, chars)) % 256)
            data += res

        a = 1
        a_len = 0
    code_ip += 1