How do I check if a string is unicode or ascii

Question

What do I have to do in Python to figure out which encoding a string has

User · Answer

Unicode is not an encoding - to quote Kumar McMillan:

If ASCII, UTF-8, and other byte strings are "text" ...

...then Unicode is "text-ness";

it is the abstract form of text

Have a read of McMillan's Unicode In Python, Completely Demystified talk from PyCon 2008, it explains things a lot better than most of the related answers on Stack Overflow.

User · Answer

One simple approach is to check if unicode is a builtin function  If so  you re in Python 2 and your string will be a string  To ensure everything is in unicode one can do   import builtins  i    cats  if  unicode  in dir builtins         True in python 2  False in 3   i   unicode i

User · Answer

For py2 py3 compatibility simply use    import six if isinstance obj  six text type

User · Answer

You could use Universal Encoding Detector  but be aware that it will just give you best guess  not the actual encoding  because it s impossible to know encoding of a string  abc  for example  You will need to get encoding information elsewhere  eg HTTP protocol uses Content-Type header for that

User · Answer

How to tell if an object is a unicode string or a byte string  You can use type or isinstance   In Python 2    gt  gt  gt  type u abc      Python 2 unicode string literal  lt type  unicode  gt   gt  gt  gt  type  abc       Python 2 byte string literal  lt type  str  gt    In Python 2  str is just a sequence of bytes  Python doesn t know what its encoding is   The unicode type is the safer way to store text  If you want to understand this more  I recommend http   farmdev com talks unicode    In Python 3    gt  gt  gt  type  abc       Python 3 unicode string literal  lt class  str  gt   gt  gt  gt  type b abc      Python 3 byte string literal  lt class  bytes  gt    In Python 3  str is like Python 2 s unicode  and is used to store text  What was called str in Python 2 is called bytes in Python 3     How to tell if a byte string is valid utf-8 or ascii  You can call decode   If it raises a UnicodeDecodeError exception  it wasn t valid    gt  gt  gt  u umlaut   b  xc3 x9c      UTF-8 representation of the letter       gt  gt  gt  u umlaut decode  utf-8   u  xdc   gt  gt  gt  u umlaut decode  ascii   Traceback  most recent call last     File   lt stdin gt    line 1  in  lt module gt  UnicodeDecodeError   ascii  codec can t decode byte 0xc3 in position 0  ordinal not in range 128

User · Answer

Note that on Python 3  it s not really fair to say any of    strs are UTFx for any x  eg  UTF8  strs are Unicode strs are ordered collections of Unicode characters   Python s str type is  normally  a sequence of Unicode code points  some of which map to characters     Even on Python 3  it s not as simple to answer this question as you might imagine   An obvious way to test for ASCII-compatible strings is by an attempted encode    Hello there   encode  ascii     gt  gt  gt  b Hello there     Hello there        encode  ascii     gt  gt  gt  Traceback  most recent call last     gt  gt  gt    File     line 4  in  lt module gt    gt  gt  gt  UnicodeEncodeError   ascii  codec can t encode character   u2603  in position 15  ordinal not in range 128    The error distinguishes the cases   In Python 3  there are even some strings that contain invalid Unicode code points    Hello there   encode  utf8     gt  gt  gt  b Hello there      udcc3  encode  utf8     gt  gt  gt  Traceback  most recent call last     gt  gt  gt    File     line 19  in  lt module gt    gt  gt  gt  UnicodeEncodeError   utf-8  codec can t encode character   udcc3  in position 0  surrogates not allowed   The same method to distinguish them is used

User · Answer

use   import six if isinstance obj  six text type    inside the six library it is represented as     if PY3      string types   str  else      string types   basestring

User · Answer

This may help someone else  I started out testing for the string type of the variable s  but for my application  it made more sense to simply return s as utf-8   The process calling return utf  then knows what it is dealing with and can handle the string appropriately   The code is not pristine  but I intend for it to be Python version agnostic without a version test or importing six   Please comment with improvements to the sample code below to help other people   def return utf s       if isinstance s  str           return s encode  utf-8       if isinstance s   int  float  complex            return str s  encode  utf-8       try          return s encode  utf-8       except TypeError          try              return str s  encode  utf-8           except AttributeError              return s     except AttributeError          return s     return s   assume it was already utf-8

User · Answer

In python 3 x all strings are sequences of Unicode characters  and doing the isinstance check for str  which means unicode string by default  should suffice   isinstance x  str    With regards to python 2 x   Most people seem to be using an if statement that has two checks  one for str and one for unicode   If you want to check if you have a  string-like  object all with one statement though  you can do the following   isinstance x  basestring

User · Answer

If your code needs to be compatible with both Python 2 and Python 3  you can t directly use things like isinstance s bytes  or isinstance s unicode  without wrapping them in either try except or a python version test  because bytes is undefined in Python 2 and unicode is undefined in Python 3   There are some ugly workarounds   An extremely ugly one is to compare the name of the type  instead of comparing the type itself   Here s an example     convert bytes  python 3  or unicode  python 2  to str if str type s        lt class  bytes  gt          only possible in Python 3     s   s decode  ascii      or  s   str s  2 -1  elif str type s        lt type  unicode  gt          only possible in Python 2     s   str s    An arguably slightly less ugly workaround is to check the Python version number  e g    if sys version info  gt    3 0 0         for Python 3     if isinstance s  bytes           s   s decode  ascii      or  s   str s  2 -1  else        for Python 2     if isinstance s  unicode           s   str s    Those are both unpythonic  and most of the time there s probably a better way

User · Answer

In Python 3  all strings are sequences of Unicode characters  There is a bytes type that holds raw bytes   In Python 2  a string may be of type str or of type unicode  You can tell which using code something like this   def whatisthis s       if isinstance s  str           print  ordinary string      elif isinstance s  unicode           print  unicode string      else          print  not a string    This does not distinguish  Unicode or ASCII   it only distinguishes Python types  A Unicode string may consist of purely characters in the ASCII range  and a bytestring may contain ASCII  encoded Unicode  or even non-textual data

[python] How do I check if a string is unicode or ascii?

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