Setting the correct encoding when piping stdout in Python

First, regarding this solution:

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

It's not practical to explicitly print with a given encoding every time. That would be repetitive and error-prone.

A better solution is to change sys.stdout at the start of your program, to encode with a selected encoding. Here is one solution I found on Python: How is sys.stdout.encoding chosen?, in particular a comment by "toka":

import sys
import codecs
sys.stdout = codecs.getwriter('utf8')(sys.stdout)

export PYTHONIOENCODING=utf-8

do the job, but can't set it on python itself ...

what we can do is verify if isn't setting and tell the user to set it before call script with :

if __name__ == '__main__':
    if (sys.stdout.encoding is None):
        print >> sys.stderr, "please set python env PYTHONIOENCODING=UTF-8, example: export PYTHONIOENCODING=UTF-8, when write to stdout."
        exit(1)

Update to reply to the comment: the problem just exist when piping to stdout . I tested in Fedora 25 Python 2.7.13

python --version
Python 2.7.13

cat b.py

#!/usr/bin/env python
#-*- coding: utf-8 -*-
import sys

print sys.stdout.encoding

running ./b.py

UTF-8

running ./b.py | less

None

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.

You may want to try changing the environment variable "PYTHONIOENCODING" to "utf_8". I have written a page on my ordeal with this problem.

Tl;dr of the blog post:

import sys, locale, os
print(sys.stdout.encoding)
print(sys.stdout.isatty())
print(locale.getpreferredencoding())
print(sys.getfilesystemencoding())
print(os.environ["PYTHONIOENCODING"])
print(chr(246), chr(9786), chr(9787))

gives you

utf_8
False
ANSI_X3.4-1968
ascii
utf_8
ö ☺ ☻