Error converting python-QRCode Module to Python 3

Question

Good Afternoon, for several days i try, to getting the Python QR-Code Module from lincolnloop running under Python3. It runs perfect on Python 2.x. - https://github.com/lincolnloop/python-qrcode

In general i'am very new to Python Programming but i think i have done my homework so far.

First Error:

 File "/usr/lib/python3.2/qrcode/util.py", line 274, in __init__

    if not isinstance(data, basestring):
NameError: global name 'basestring' is not defined

So basestring didnt exist in Python3 anymore i fix this with this Code Statement found here. - https://github.com/oxplot/fysom/issues/1

try:
    unicode = unicode
except NameError:
    # 'unicode' is undefined, must be Python 3
    str = str
    unicode = str
    bytes = bytes
    basestring = (str,bytes)
else:
    # 'unicode' exists, must be Python 2
    str = str
    unicode = unicode
    bytes = str
    basestring = basestring

So the next Error comes up.

  File "/usr/lib/python3.2/qrcode/util.py", line 285, in __init__
    elif re.match('^[%s]*$' % re.escape(ALPHA_NUM), data):
  File "/usr/lib/python3.2/re.py", line 153, in match
    return _compile(pattern, flags).match(string)
TypeError: can't use a string pattern on a bytes-like object

So i try the solution found here - Python TypeError on regex and change the following code from:

elif re.match('^[%s]*$' % re.escape(ALPHA_NUM), data):

to:

elif re.match(b'^[%s]*$' % re.escape(ALPHA_NUM), data): 

to Handle the RegEx in Binary Mode. But this throws the next execption in the same line of Code.

    elif re.match(b'^[%s]*$' % re.escape(ALPHA_NUM), data):
TypeError: unsupported operand type(s) for %: 'bytes' and 'str'

I also try to change

ALPHA_NUM = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:'

to

ALPHA_NUM = b'0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:'

But this makes no changes to the Execption.

So this indicates for me the same error as the one before, and anywhere in the code must be this type error wether its bytes or string type. But i cant find it.

I know the whole script is very complex for diving into python, but for my project, i need a working QR Code generator.

Can somebody give me a clue? Thanks in advance!

Answer 1

You can't use the % operator with bytes objects. Is the data you are dealing with now really binary data, or is it text? If it is text, you should really handle it as strings, not as bytes.

Also, talk to the authors of the module. They might have done much of the porting already, or they might be willing to help. Thirdly, read python3porting.com, a free book on the topic.

Handling both Unicode and bytes data is the difficult part of the porting. You will have to make sure you are consistently using one or the other, and it is often quite a pain to get right.