QByteArray.data() returns python`s 'str' object.
But if there is zero byte in QByteArray.data(), all data will be cutted just
before this zero-byte.
For example:
    >>>b = QByteArray("Preved\x00Medved!")
    >>>b.data()  
    "Preved" # invalid!!!
    >>>[c for c in b] 
    ['P','r','e','v','e','d','','M','e','d','v','e','d','!'] # normal

Using s.data() will give us only "Preved".
This is correct for C language (I suppose the bug is in using 'strlen()' C
function), but incorrect for Python: 
    >>>s = 'Preved\x00Medved!'
    >>>s, s[6], ord(s[6])
    ("Preved\x00Medved!", '\x00', 0)

so the only way to get QByteArray`s data is following madness:
    >>>''.join([a if a!='' else '\x00' for a in b])
    "Preved\x00Medved!"