Python - Get a list of all the encodings python can encode to

Question

I am writing a script that will try encoding bytes into many different encodings in python 2.6. This page http://www.python.org/doc/2.6/library/codecs.html?highlight=cp1250#id3 lists all the encodings that python can encode to. Rather than copy & paste that, is there some way to get a list of available encodings that I can iterate over?

UPDATE: The reason I'm trying to do this is because a user has some text that is not encoded correctly. There are funny characters. I know the unicode character that's messing it up. I want to be able to give them an answer like "You're text editor is interpreting that string as X encoding, not Y encoding". I thought I would try to decode that character into an encoding, then back to another encoding, and see if we get the same character sequence.

i.e.: something like this

for encoding1, encoding2 in itertools.permutation(encodinglist(), 2):
  try:
    unicode_string = my_unicode_character.encode(encoding1).decode(encoding2)
  except:
    pass

Answer 1

You could use a technique to list all modules in the encodings package.

import pkgutil
import encodings

false_positives = set(["aliases"])

found = set(name for imp, name, ispkg in pkgutil.iter_modules(encodings.__path__) if not ispkg)
found.difference_update(false_positives)
print found

Answer 2

I do not know if there is such method/functionality in codecs module, but if you see encoding/init.py, serach function searches thru encodings modules folder. so you may do the same e.g.

>>> os.listdir(os.path.dirname(encodings.__file__))
['cp500.pyc', 'utf_16_le.py', 'gb18030.py', 'mbcs.pyc', 'undefined.pyc', 'idna.pyc', 'punycode.pyc', 'cp850.py', 'big5hkscs.pyc', 'mac_arabic.py', '__init__.pyc', 'string_escape.py', 'hz.py', 'cp037.py', 'cp737.py', 'iso8859_5.pyc', 'iso8859_13.pyc', 'cp861.pyc', 'cp862.py', 'iso8859_9.pyc', 'cp949.py', 'base64_codec.pyc', 'koi8_r.py', 'iso8859_2.py', 'ptcp154.pyc', 'uu_codec.pyc', 'mac_croatian.pyc', 'charmap.pyc', 'iso8859_15.pyc', 'euc_jp.py', 'cp1250.py', 'iso8859_10.pyc', 'koi8_r.pyc', 'unicode_escape.pyc', 'cp863.pyc', 'iso8859_4.pyc', 'cp852.py', 'unicode_internal.py', 'big5hkscs.py', 'cp1257.pyc', 'cp1254.py', 'shift_jisx0213.py', 'shift_jis.pyc', 'cp869.pyc', 'hp_roman8.py', 'iso8859_4.py', 'cp775.py', 'cp1251.py', 'mac_cyrillic.pyc', 'mac_greek.pyc', 'mac_roman.pyc', 'iso8859_11.pyc', 'iso8859_6.py', 'utf_8_sig.py', 'iso8859_3.py', 'iso2022_jp_1.py', 'ascii.py', 'cp1026.pyc', 'cp1250.pyc', 'cp950.py', 'raw_unicode_escape.py', 'euc_jis_2004.pyc', 'cp775.pyc', 'euc_kr.py', 'mac
_greek.py', 'big5.pyc', 'shift_jis_2004.pyc', 'gbk.pyc', 'cp1254.pyc', 'cp1255.pyc', 'cp855.pyc', 'string_escape.pyc', 'cp949.pyc', 'cp1258.pyc', 'iso8859_3.pyc', 'mac_iceland.pyc', 'cp1251.pyc', 'cp860.py', 'cp856.py', 'cp874.py', 'iso2022_kr.py', 'cp856.pyc', 'rot_13.py', 'palmos.py', 'iso2022_jp_2.pyc', 'mac_farsi.py', 'koi8_u.pyc', 'cp1256.py', 'iso8859_10.py', 'tis_620.py', 'iso8859_14.pyc', 'cp1253.py', 'cp1258.py', 'cp437.py', 'cp862.pyc', 'mac_turkish.py', 'undefined.py', 'euc_kr.pyc', 'gb18030.pyc', 'aliases.pyc', 'iso8859_9.py', 'uu_codec.py', 'gbk.py', 'quopri_codec.pyc', 'iso8859_7.py', 'mac_iceland.py', 'iso8859_2.pyc', 'euc_jis_2004.py', 'iso2022_jp_3.pyc', 'cp874.pyc', '__init__.py', 'mac_roman.py', 'iso8859_16.py', 'cp866.py', 'unicode_internal.pyc', 'mac_turkish.pyc', 'johab.pyc', 'cp037.pyc', 'punycode.py', 'cp1253.pyc', 'euc_jisx0213.pyc', 'iso2022_jp_2004.pyc', 'iso2022_kr.pyc', 'zlib_codec.pyc', 'cp932.py', 'cp1255.py', 'iso2022_jp_1.pyc', 'cp857.pyc', 'cp424.pyc',
 'iso2022_jp_2.py', 'iso2022_jp.pyc', 'mbcs.py', 'utf_8.py', 'palmos.pyc', 'cp1252.pyc', 'aliases.py', 'quopri_codec.py', 'latin_1.pyc', 'iso2022_jp.py', 'zlib_codec.py', 'cp1026.py', 'cp860.pyc', 'cp1252.py', 'hex_codec.pyc', 'iso8859_1.pyc', 'cp850.pyc', 'cp861.py', 'iso8859_15.py', 'cp865.pyc', 'hp_roman8.pyc', 'iso8859_7.pyc', 'mac_latin2.py', 'iso8859_11.py', 'mac_centeuro.pyc', 'iso8859_6.pyc', 'ascii.pyc', 'mac_centeuro.py', 'iso2022_jp_3.py', 'bz2_codec.py', 'mac_arabic.pyc', 'euc_jisx0213.py', 'tis_620.pyc', 'shift_jis_2004.py', 'utf_8.pyc', 'cp855.py', 'mac_romanian.pyc', 'iso8859_8.py', 'cp869.py', 'ptcp154.py', 'utf_16_be.py', 'iso2022_jp_ext.pyc', 'bz2_codec.pyc', 'base64_codec.py', 'latin_1.py', 'charmap.py', 'hz.pyc', 'cp950.pyc', 'cp875.pyc', 'cp1006.pyc', 'utf_16.py', 'shift_jisx0213.pyc', 'cp424.py', 'cp932.pyc', 'iso8859_5.py', 'mac_romanian.py', 'utf_8_sig.pyc', 'iso8859_1.py', 'cp875.py', 'cp437.pyc', 'cp865.py', 'utf_7.py', 'utf_16_be.pyc', 'rot_13.pyc', 'euc_jp.p
yc', 'raw_unicode_escape.pyc', 'iso8859_8.pyc', 'utf_16.pyc', 'iso8859_14.py', 'iso8859_16.pyc', 'cp852.pyc', 'cp737.pyc', 'mac_croatian.py', 'mac_latin2.pyc', 'iso2022_jp_ext.py', 'cp1140.py', 'mac_cyrillic.py', 'cp1257.py', 'cp500.py', 'cp1140.pyc', 'shift_jis.py', 'unicode_escape.py', 'cp864.py', 'cp864.pyc', 'cp857.py', 'hex_codec.py', 'mac_farsi.pyc', 'idna.py', 'johab.py', 'utf_7.pyc', 'cp863.py', 'iso8859_13.py', 'koi8_u.py', 'gb2312.pyc', 'cp1256.pyc', 'cp866.pyc', 'iso2022_jp_2004.py', 'utf_16_le.pyc', 'gb2312.py', 'cp1006.py', 'big5.py']

but as any body can register a codec, so that won't be exhaustive list.

Answer 3

Probably you can do this:

from encodings.aliases import aliases
print aliases.keys()

Answer 4

Unfortunately encodings.aliases.aliases.keys() is NOT an appropriate answer.

aliases(as one would/should expect) contains several cases where different keys are mapped to the same value e.g. 1252 and windows_1252 are both mapped to cp1252. You could save time if instead of aliases.keys() you use set(aliases.values()).

BUT THERE'S A WORSE PROBLEM: aliases doesn't contain codecs that don't have aliases (like cp856, cp874, cp875, cp737, and koi8_u).

>>> from encodings.aliases import aliases
>>> def find(q):
...     return [(k,v) for k, v in aliases.items() if q in k or q in v]
...
>>> find('1252') # multiple aliases
[('1252', 'cp1252'), ('windows_1252', 'cp1252')]
>>> find('856') # no codepage 856 in aliases
[]
>>> find('koi8') # no koi8_u in aliases
[('cskoi8r', 'koi8_r')]
>>> 'x'.decode('cp856') # but cp856 is a valid codec
u'x'
>>> 'x'.decode('koi8_u') # but koi8_u is a valid codec
u'x'
>>>

It's also worth noting that however you obtain a full list of codecs, it may be a good idea to ignore the codecs that aren't about encoding/decoding character sets, but do some other transformation e.g. zlib, quopri, and base64.

Which brings us to the question of WHY you want to "try encoding bytes into many different encodings". If we know that, we may be able to steer you in the right direction.

For a start, that's ambiguous. One DEcodes bytes into unicode, and one ENcodes unicode into bytes. Which do you want to do?

What are you really trying to achieve: Are you trying to determine which codec to use to decode some incoming bytes, and plan to attempt this with all possible codecs? [note: latin1 will decode anything] Are you trying to determine the language of some unicode text by trying to encode it with all possible codecs? [note: utf8 will encode anything].

Answer 5

Maybe you should try using the Universal Encoding Detector (chardet) library instead of implementing it yourself.

>>> import chardet
>>> s = '\xe2\x98\x83' # ☃
>>> chardet.detect(s)
{'confidence': 0.505, 'encoding': 'utf-8'}