String value decode utf-8 - python-2.7

Question

I want to decode string values ​​to utf-8. But it doesn't change.
So, here is my code:
self.textEdit_3.append(str(self.new_header).decode("utf-8") + "\n")
The result image is here:
The original output value is:
['matchkey', 'a', 'b', 'd', '안녕'] # 안녕 is Korean Language
I changed the default encoding for encoding / decoding with unicode to utf-8 instead of ascii. On the first line I added this code:
import sys
reload(sys)
sys.setdefaultencoding('utf-8')
Why doesn't the string value change?

Answer 1

You can fix your code like this:
header = str(self.new_header).decode('string-escape').decode("utf-8")
self.textEdit_3.append(header + "\n")
You do not need the setdefaultencoding lines.
Expanantion:
The original value is a list containing byte-strings:
>>> value = ['matchkey', 'a', 'b', 'd', '안녕']
>>> value
['matchkey', 'a', 'b', 'd', '\xec\x95\x88\xeb\x85\x95']
If you convert this list with str, it will use repr on all the list elements:
>>> strvalue = str(value)
>>> strvalue
"['matchkey', 'a', 'b', 'd', '\\xec\\x95\\x88\\xeb\\x85\\x95']"
The repr parts can be decoded like this:
>>> strvalue = strvalue.decode('string-escape')
>>> strvalue
"['matchkey', 'a', 'b', 'd', '\xec\x95\x88\xeb\x85\x95']"
and this can now be decoded to unicode like this:
>>> univalue = strvalue.decode('utf-8')
>>> univalue
u"['matchkey', 'a', 'b', 'd', '\uc548\ub155']"
>>> print univalue
['matchkey', 'a', 'b', 'd', '안녕']
PS:
Regarding the problems reading files with a utf-8 bom, please test this script:
# -*- coding: utf-8 -*-
import os, codecs, tempfile
text = u'a,b,d,안녕'
data = text.encode('utf-8-sig')
print 'text:', repr(text), len(text)
print 'data:', repr(data), len(data)
f, path = tempfile.mkstemp()
print 'write:', os.write(f, data)
os.close(f)
with codecs.open(path, 'r', encoding='utf-8-sig') as f:
string = f.read()
print 'read:', repr(string), len(string), string == text