3bf.py

#!/usr/bin/env python3

bits_to_symbols = {
    0b000: '<',
    0b001: '>',
    0b010: '[',
    0b011: ']',
    0b100: '+',
    0b101: '-',
    0b110: ',',
    0b111: '.',
}

symbols_to_bits = {value:key for (key, value) in bits_to_symbols.items()}

def bf_compress(code):
    pad = len(code) % 8
    lpad = pad//3
    rpad = pad - lpad
    b_code = '{:03b}'.format(symbols_to_bits['<'])*lpad
    for c in code:
        b_code += '{:03b}'.format(symbols_to_bits[c])
    b_code += '0'*rpad
    out = b''
    for i in range(len(b_code)//8):
        out += bytes([int(b_code[8*i:8*i+8], 2)])
    return out

def bf_decompress(code):
    b_code = ''.join("{:08b}".format(x) for x in code)
    out = ''
    for i in range(len(b_code)//3):
        triplet = b_code[3*i:3*i+3]
        if len(triplet) < 3:
            break
        out += bits_to_symbols[int(triplet, 2)]
    return out.lstrip('<')

if __name__ == '__main__':
    print(bf_compress('>+'))
    print(bf_decompress(bf_compress('>+')))