Python – Figuring out unicode: ‘ascii’ codec can’t decode

pythonunicode

I currently use Sublime 2 and run my python code there.
When I try to run this code. I get this error:

UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position
6: ordinal not in range(128)

# -*- coding: utf-8 -*-  
s = unicode('abcdefö') 
print s

I have been reading the python documentation on unicode and as far as I understand this should work, or is it the console that's not working

Edit: Using s = u'abcdefö' as a string produces almost the same result. The result I get is

UnicodeEncodeError: 'ascii' codec can't encode character u'\xf6' in
position 6: ordinal not in range(128)

Best Answer

What happens is that unicode('abcdefö') tries to decode the encoded string to unicode during runtime. The coding: utf-8 line only tells Python that the source file is encoded in utf8. When the script runs it has been compiled and string has been stored as a encoded string. So when Python tries to decode the string it uses ascii by default. As the string is actually utf8 encoded this fails.

You can do s = u'abcdefö' which tells the compiler to decode the string with the encoding declared for the file and store it as unicode. s = unicode('abcdefö', 'utf8') or s = 'abcdefö'.decode('utf8') would do the same thing during runtime.

However does not necessarily mean that you can print s now. First the internal unicode string has to be encoded in a character set that the stdout (the console/editor/IDE) can actually display. Sadly often Python fails at figuring out the right character set and defaults to ascii again and you get an error when the string contains non-ascii characters. The Python Wiki knows a few ways to set up stdout properly.

Related Solutions

Python – Setting the correct encoding when piping stdout in Python

Your code works when run in an script because Python encodes the output to whatever encoding your terminal application is using. If you are piping you must encode it yourself.

A rule of thumb is: Always use Unicode internally. Decode what you receive, and encode what you send.

# -*- coding: utf-8 -*-
print u"åäö".encode('utf-8')

Another didactic example is a Python program to convert between ISO-8859-1 and UTF-8, making everything uppercase in between.

import sys
for line in sys.stdin:
    # Decode what you receive:
    line = line.decode('iso8859-1')

    # Work with Unicode internally:
    line = line.upper()

    # Encode what you send:
    line = line.encode('utf-8')
    sys.stdout.write(line)

Setting the system default encoding is a bad idea, because some modules and libraries you use can rely on the fact it is ASCII. Don't do it.

Python – Write to UTF-8 file in Python

I believe the problem is that codecs.BOM_UTF8 is a byte string, not a Unicode string. I suspect the file handler is trying to guess what you really mean based on "I'm meant to be writing Unicode as UTF-8-encoded text, but you've given me a byte string!"

Try writing the Unicode string for the byte order mark (i.e. Unicode U+FEFF) directly, so that the file just encodes that as UTF-8:

import codecs

file = codecs.open("lol", "w", "utf-8")
file.write(u'\ufeff')
file.close()

(That seems to give the right answer - a file with bytes EF BB BF.)

EDIT: S. Lott's suggestion of using "utf-8-sig" as the encoding is a better one than explicitly writing the BOM yourself, but I'll leave this answer here as it explains what was going wrong before.

Best Answer

Related Solutions

Python – Setting the correct encoding when piping stdout in Python

Python – Write to UTF-8 file in Python

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