NameError: global name 'unicode' is not defined - in Python 3

Question

I am trying to use a Python package called bidi. In a module in this package (algorithm.py) there are some lines that give me error, although it is part of the package.

Here are the lines:

# utf-8 ? we need unicode
if isinstance(unicode_or_str, unicode):
    text = unicode_or_str
    decoded = False
else:
    text = unicode_or_str.decode(encoding)
    decoded = True

and here is the error message:

Traceback (most recent call last):
  File "<pyshell#25>", line 1, in <module>
    bidi_text = get_display(reshaped_text)
  File "C:\Python33\lib\site-packages\python_bidi-0.3.4-py3.3.egg\bidi\algorithm.py",   line 602, in get_display
    if isinstance(unicode_or_str, unicode):
NameError: global name 'unicode' is not defined

How should I re-write this part of the code so it works in Python3? Also if anyone have used bidi package with Python 3 please let me know if they have found similar problems or not. I appreciate your help.

Bechuanaland

Answer 1

Python 3 renamed the unicode type to str, the old str type has been replaced by bytes.

if isinstance(unicode_or_str, str):
    text = unicode_or_str
    decoded = False
else:
    text = unicode_or_str.decode(encoding)
    decoded = True

You may want to read the Python 3 porting HOWTO for more such details. There is also Lennart Regebro's Porting to Python 3: An in-depth guide, free online.

Last but not least, you could just try to use the 2to3 tool to see how that translates the code for you.

Slime

So should I write: if isinstance(unicode_or_str, str)? How about 'unicode_or_str'? – Bechuanaland

The variable name doesn't much matter here; if isinstance(unicode_or_str, str) should just work. Renaming the variable name is optional. – Slime

Answer 2

If you need to have the script keep working on python2 and 3 as I did, this might help someone

import sys
if sys.version_info[0] >= 3:
    unicode = str

and can then just do for example

foo = unicode.lower(foo)

Hesperidin

This is the right idea, nice answer. Just to add a detail, if you are using the six library to manage Python 2/3 compatibility, you can make this: if six.PY3: unicode = str instead of sys.version_info stuff. This is also very helpful for preventing linter errors related to unicode being undefined in Python 3, without needing special linter rule exemptions. – Emphasize

Answer 3

You can use the six library to support both Python 2 and 3:

import six
if isinstance(value, six.string_types):
    handle_string(value)

Tomtom

Answer 4

One can replace unicode with u''.__class__ to handle the missing unicode class in Python 3. For both Python 2 and 3, you can use the construct

isinstance(unicode_or_str, u''.__class__)

or

type(unicode_or_str) == type(u'')

Depending on your further processing, consider the different outcome:

Python 3

>>> isinstance(u'text', u''.__class__)
True
>>> isinstance('text', u''.__class__)
True

Python 2

>>> isinstance(u'text', u''.__class__)
True
>>> isinstance('text', u''.__class__)
False

Crewel

Answer 5

Hope you are using Python 3 , Str are unicode by default, so please Replace Unicode function with String Str function.

if isinstance(unicode_or_str, str):    ##Replaces with str
    text = unicode_or_str
    decoded = False

Alfrediaalfredo

that doesn't preserve BC like the answer from @Tomtom Please consider retracting or updating your answer. There is no reason to leave python2 users behind or have breaking python3 – Laval

Answer 6

If a 3rd-party library uses unicode and you can't change their source code, the following monkey patch will work to use str instead of unicode in the module:

import <module>
<module>.unicode = str

Imperfect

Answer 7

you can use this in python2 or python3

type(value).__name__ == 'unicode':

Peirce