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usage of <string>.encode('utf-8','xmlcharrefreplace')?

P: n/a
Well, as usual I am confused by unicode encoding errors.

I have a string with problematic characters in it which I'd like to
put into a postgresql table.
That results in a postgresql error so I am trying to fix things with
<string>.encode
>>s = 'he Company\xef\xbf\xbds ticker'
print s
he Company�s ticker
>>>
Trying for an encode:
>>print s.encode('utf-8')
Traceback (most recent call last):
File "<input>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xef in position
10: ordinal not in range(128)

OK, that's pretty much as expected, I know this is not valid utf-8.
But I should be able to fix this with the errors parameter of the
encode method.
>>error_replace = 'xmlcharrefreplace'
>>print s.encode('utf-8',error_replace)
Traceback (most recent call last):
File "<input>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xef in position
10: ordinal not in range(128)

Same exact error I got without the errors parameter.

Did I mistype the error handler name? Nope.
>>codecs.lookup_error(error_replace)
<built-in function xmlcharrefreplace_errors>

Same results with 'ignore' as an error handler.
>>print s.encode('utf-8','ignore')
Traceback (most recent call last):
File "<input>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xef in position
10: ordinal not in range(128)

And with a bogus error handler:

print s.encode('utf-8','bogus')
Traceback (most recent call last):
File "<input>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xef in position
10: ordinal not in range(128)

This all looks unusually complicated for Python.
Am I missing something incredibly obvious?
How does one use the errors parameter on strings' encode method?

Also, why are the exceptions above complaining about the 'ascii' codec
if I am asking for 'utf-8' conversion?

Version and environment below. Should I try to update my python from
somewhere?

./$ python
Python 2.5.1 (r251:54863, Oct 5 2007, 13:36:32)
[GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2

Cheers
Feb 19 '08 #1
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4 Replies


P: n/a
On Mon, 18 Feb 2008 21:36:17 -0800 (PST), J Peyret wrote
Well, as usual I am confused by unicode encoding errors.

I have a string with problematic characters in it which I'd like to
put into a postgresql table.
That results in a postgresql error so I am trying to fix things with
<string>.encode
>s = 'he Company\xef\xbf\xbds ticker'
print s
he [UTF-8?]Company�s ticker
>>

Trying for an encode:
>print s.encode('utf-8')
Traceback (most recent call last):
File "<input>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xef in position
10: ordinal not in range(128)

OK, that's pretty much as expected, I know this is not valid utf-8.
Actually, the string *is* valid UTF-8, but you're confused about encoding and
decoding. Encoding is the process of turning a Unicode object into a byte
string. Decoding is the process of turning a byte string into a Unicode object.

You need to decode your byte string into a Unicode object, and then encode the
result to a byte string in a different encoding. For example:
>>s = 'he Company\xef\xbf\xbds ticker'
s.decode("utf-8").encode("ascii", "xmlcharrefreplace")
'he Company�s ticker'

By the way, whether this is the correct fix for your PostgreSQL error is not
clear, since you kept that error message a secret for some reason. There could
be a better solution than transcoding the string in this way, but we won't
know until you show us the actual error you're trying to fix. At the moment,
it's like showing you the best way to inflate a tire with a hammer.

Hope this helps,

--
Carsten Haese
http://informixdb.sourceforge.net

Feb 19 '08 #2

P: n/a
To clarify a couple of points:

On Feb 18, 11:38*pm, 7stud <bbxx789_0...@yahoo.comwrote:
>*A unicode string looks like this:

s = u'\u0041'

but your string looks like this:

s = 'he Company\xef\xbf\xbds ticker'

Note that there is no 'u' in front of your string. *
That means your string is a regular string.

If a python function requires a unicode string and a unicode string
isn't provided..
For example: encode().
One last point: you can't display a unicode string. The very act of
trying to print a unicode string causes it to be converted to a
regular string. If you try to display a unicode string without
explicitly encode()'ing it first, i.e. converting it to a regular
string using a specified secret code--a so called 'codec', python will
implicitly attempt to convert the unicode string to a regular string
using the default codec, which is usually set to ascii.

Feb 19 '08 #3

P: n/a
On Feb 18, 10:54 pm, 7stud <bbxx789_0...@yahoo.comwrote:
One last point: you can't display a unicode string. The very act of
trying to print a unicode string causes it to be converted to a
regular string. If you try to display a unicode string without
explicitly encode()'ing it first, i.e. converting it to a regular
string using a specified secret code--a so called 'codec', python will
implicitly attempt to convert the unicode string to a regular string
using the default codec, which is usually set to ascii.
Yes, the string above was obtained by printing, which got it into
ASCII format, as you picked up.
Something else to watch out for when posting unicode issues.

The solution I ended up with was

1) Find out the encoding in the data file.

In Ubuntu's gedit editor, menu 'Save As...' displays the encoding at
the bottom of the save prompt dialog.

ISO-8859-15 in my case.

2) Look up encoding corresponding to ISO-8859-15 at

http://docs.python.org/lib/standard-encodings.html

3) Applying the decode/encode recipe suggested previously, for which I
do understand the reason now.

#converting rawdescr
#from ISO-8859-15 (from the file)
#to UTF-8 (what postgresql wants)
#no error handler required.
decodeddescr = rawdescr.decode('iso8859_15').encode('utf-8')

postgresql insert is done using decodeddescr variable.

Postgresql is happy, I'm happy.
Feb 19 '08 #4

P: n/a
On Feb 19, 12:15*am, J Peyret <jpey...@gmail.comwrote:
On Feb 18, 10:54 pm, 7stud <bbxx789_0...@yahoo.comwrote:
One last point: you can't display a unicode string. *The very act of
trying to print a unicode string causes it to be converted to a
regular string. *If you try to display a unicode string without
explicitly encode()'ing it first, i.e. converting it to a regular
string using a specified secret code--a so called 'codec', python will
implicitly attempt to convert the unicode string to a regular string
using the default codec, which is usually set to ascii.

Yes, the string above was obtained by printing, which got it into
ASCII format, as you picked up.
Something else to watch out for when posting unicode issues.

The solution I ended up with was

1) Find out the encoding in the data file.

In Ubuntu's gedit editor, menu 'Save As...' displays the encoding at
the bottom of the save prompt dialog.

ISO-8859-15 in my case.

2) Look up encoding corresponding to ISO-8859-15 at

http://docs.python.org/lib/standard-encodings.html

3) Applying the decode/encode recipe suggested previously, for which I
do understand the reason now.

#converting rawdescr
#from ISO-8859-15 (from the file)
#to UTF-8 (what postgresql wants)
#no error handler required.
decodeddescr = rawdescr.decode('iso8859_15').encode('utf-8')

postgresql insert is done using decodeddescr variable.

Postgresql is happy, I'm happy.
Or, you can cheat. If you are reading from a file, you can make set
it up so any string that you read from the file automatically gets
converted from its encoding to another encoding. You don't even have
to be aware of the fact that a regular string has to be converted into
a unicode string before it can be converted to a regular string with a
different encoding. Check out the codecs module and the EncodedFile()
function:

import codecs

s = 'he Company\xef\xbf\xbds ticker'

f = open('data2.txt', 'w')
f.write(s)
f.close()

f = open('data2.txt')
f_special = codecs.EncodedFile(f, 'utf-8', 'iso8859_15') #file, new
encoding, file's encoding
print f_special.read() #If your display device understands utf-8, you
will see the troublesome character displayed.
#Are you sure that character is legitimate?

f.close()
f_special.close()


Feb 19 '08 #5

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