'str' does not support the buffer interface Python3 from Python2

Question

Hi have this two funtions in Py2 works fine but it doesn´t works on Py3

def encoding(text, codes):
    binary = ''
    f = open('bytes.bin', 'wb')
    for c in text:
        binary += codes[c]
    f.write('%s' % binary)
    print('Text in binary:', binary)
    f.close()
    return len(binary)

def decoding(codes, large):
    f = file('bytes.bin', 'rb')
    bits = f.read(large)
    tmp = ''
    decode_text = ''
    for bit in bits:
        tmp += bit
        if tmp in fordecodes:
            decode_text += fordecodes[tmp]
            tmp = ''
    f.close()
    return decode_text

The console ouputs this:

Traceback (most recent call last):
  File "Practica2.py", line 83, in <module>
    large = encoding(text, codes)
  File "Practica2.py", line 56, in encoding
    f.write('%s' % binary)
TypeError: 'str' does not support the buffer interface

you need to cast to bytes or open in "wt" mode if using python 3.4 — Padraic Cunningham
– Padraic Cunningham, Commented Nov 15, 2014 at 12:04
possible duplicate of TypeError: 'str' does not support the buffer interface — kenorb
– kenorb, Commented May 3, 2015 at 13:55

SuperBiasedMan · Accepted Answer · 2015-09-16 11:20:57Z

21

The fix was simple for me

Use

f = open('bytes.bin', 'w')

instead of

f = open('bytes.bin', 'wb')

In python 3 'w' is what you need, not 'wb'.

edited Sep 16, 2015 at 11:20

SuperBiasedMan

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answered May 27, 2015 at 11:30

Jimmy

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Comments

ekhumoro · Accepted Answer · 2014-11-15 19:29:19Z

13

In Python 2, bare literal strings (e.g. 'string') are bytes, whereas in Python 3 they are unicode. This means if you want literal strings to be treated as bytes in Python 3, you always have to explicitly mark them as such.

So, for instance, the first few lines of the encoding function should look like this:

binary = b''
f = open('bytes.bin', 'wb')
for c in text:
    binary += codes[c]
f.write(b'%s' % binary)

and there are a few lines in the other function which need similar treatment.

See Porting to Python 3, and the section Bytes, Strings and Unicode for more details.

edited Nov 15, 2014 at 19:29

answered Nov 15, 2014 at 19:23

ekhumoro

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