How to read a string in a bitstream in Python

Question

I'm writing the following string in my output file:

bitstream.add("stri", 32)

where

def add(self, data, length):
    s = ''
    if (type(data) == str):
        for char in data:
            b = bin(ord(char))[2:]
            s = s + "{:0>8}".format(b)
    else:
        s = bin(data)[2:]
        if (len(s) < length):
            resto = length - len(s)
            for _ in range(0, resto):
                s = '0' + s
    s = s[0:length]
    self.cache = self.cache + s
    self.flush()

Later on I need to read the string from the output file. I use Python struct unpack module as follows:

   from struct import unpack
   key_length_bytes = 32
   key = ""
   for _ in range(0, key_length_bytes):
      carattere = chr(unpack('>B', in_file.read(1))[0])
      key = "%s%s" (key, carattere)

I get

key = "%s%s" (key, carattere)
TypeError: 'str' object is not callable

Thank you for any help you could provide.

read this - stackoverflow.com/questions/6039605/…

Sid
– Sid

2019-09-16 09:31:39 +00:00
Commented Sep 16, 2019 at 9:31 — Sid
– Sid, Commented Sep 16, 2019 at 9:31

doca · Accepted Answer · 2019-09-16 09:32:31Z

2

You're missing a % sign. key = "%s%s" (key, carattere) needs to be changed into

key = "%s%s" % (key, carattere)

answered Sep 16, 2019 at 9:32

doca

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1 Comment

user123892 Over a year ago

Thank you, problem solved! I also edited the question since the loop to read the string was not correct.

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