handling unicode data

[Filipe]

Hi all,

I'm starting to learn python but am having some difficulties with how
it handles the encoding of data I'm reading from a database. I'm using
pymssql to access data stored in a SqlServer database, and the
following is the script I'm using for testing purposes.

-----------------------------------------------------------------------------
import pymssql

mssqlConnection =
pymssql.connect(host='localhost',user='sa',password='password',database='TestDB')
cur = mssqlConnection.cursor()
query="Select ID, Term from TestTable where ID > 200 and ID < 300;"
cur.execute(query)
row = cur.fetchone()
results = []
while row is not None:
term = row[1]
print type(row[1])
print term
results.append(term)
row = cur.fetchone()
cur.close()
mssqlConnection.close()
print results
-----------------------------------------------------------------------------

In the console output, for a record where I expected to see "França"
I'm getting the following:

"<type 'str'>" - When I print the type (print type(row[1]))
"Fran+a" - When I print the "term" variable (print term)
"Fran\xd8a" - When I print all the query results (print results)


The values in "Term" column in "TestTable" are stored as unicode (the
column's datatype is nvarchar), yet, the python data type of the values
I'm reading is not unicode.
It all seems to be an encoding issue, but I can't see what I'm doing
wrong..
Any thoughts?

thanks in advance,
Filipe

 

[Fredrik Lundh]

In the console output, for a record where I expected to see "França"
I'm getting the following:

"<type 'str'>" - When I print the type (print type(row[1]))
"Fran+a" - When I print the "term" variable (print term)
"Fran\xd8a" - When I print all the query results (print results)

The values in "Term" column in "TestTable" are stored as unicode (the
column's datatype is nvarchar), yet, the python data type of the values
I'm reading is not unicode.
It all seems to be an encoding issue, but I can't see what I'm doing
wrong..

looks like the DB-API driver returns 8-bit ISO-8859-1 strings instead of Unicode
strings. there might be some configuration option for this; see

in worst case, you could do something like

def unicodify(value):
if isinstance(value, str):
value = unicode(value, "iso-8859-1")
return value

term = unicodify(row[1])

but it's definitely better if you can get the DB-API driver to do the right thing.

</F>

 

[=?ISO-8859-1?Q?=22Martin_v=2E_L=F6wis=22?=]

looks like the DB-API driver returns 8-bit ISO-8859-1 strings instead of Unicode
strings. there might be some configuration option for this; see

Where did you want to point the OP here?

in worst case, you could do something like

def unicodify(value):
if isinstance(value, str):
value = unicode(value, "iso-8859-1")
return value

term = unicodify(row[1])

but it's definitely better if you can get the DB-API driver to do the right thing.

It seems pymssql does not support such a thing.

Also, it appears that DB-Library (the API used by pymssql) always
returns CP_ACP characters (unless ANSI-to-OEM conversion is enabled);
so the "right" encoding to use is "mbcs".

Notice that Microsoft plans to abandon DB-Library, so it might be
best to switch to a different module for SQL Server access.

Regards,
Martin

 

[Filipe]

Hi Fredrik,

Thanks for the reply.
Instead of:
term = row[1]
I tried:
term = unicode(row[1], "iso-8859-1")

but the following error was returned when printing "term":
Traceback (most recent call last):
File "test.py", line 11, in ?
print term
File "c:\Program Files\Python24\lib\encodings\cp437.py", line 18, in
encode
return codecs.charmap_encode(input,errors,encoding_map)
UnicodeEncodeError: 'charmap' codec can't encode character u'\xd8' in
position 31: character maps to <undefined>

Is it possible some unicode strings are not printable to the console?
It's odd, because I can manually write in the console the same string
I'm trying to print.
I also tried other encodings, besides iso-8859-1, but got the same
error.

Do you think this has something to do with the DB-API driver? I don't
even know where to start if I have to change something in there :|

Cheers,
Filipe

 

[Fredrik Lundh]

Thanks for the reply.
Instead of:
term = row[1]
I tried:
term = unicode(row[1], "iso-8859-1")

but the following error was returned when printing "term":
Traceback (most recent call last):
File "test.py", line 11, in ?
print term
File "c:\Program Files\Python24\lib\encodings\cp437.py", line 18, in
encode
return codecs.charmap_encode(input,errors,encoding_map)
UnicodeEncodeError: 'charmap' codec can't encode character u'\xd8' in
position 31: character maps to <undefined>

works for me, given your example:
u'Fran\xd8a'

what does

print repr(row[1])

print in this case ?

</F>

 

[Filipe]

Hi,

Also, it appears that DB-Library (the API used by pymssql) always
returns CP_ACP characters (unless ANSI-to-OEM conversion is enabled);
so the "right" encoding to use is "mbcs".

do you mean using something like the following line?
term = unicode(row[1], "mbcs")

What do you mean by "ANSI-to-OEM conversion is enabled"? (sorry, I'm
quite a newbie to python)

Notice that Microsoft plans to abandon DB-Library, so it might be
best to switch to a different module for SQL Server access.

I've done some searching and settled for pymssql, but it's not too late
to change yet.
I've found these options to connect to a MSSqlServer database:

Pymssql
http://pymssql.sourceforge.net/

ADODB for Python (windows only)
http://phplens.com/lens/adodb/adodb-py-docs.htm

SQLServer for Python (discontinued?)
http://www.object-craft.com.au/projects/mssql/

mxODBC (commercial license)
http://www.egenix.com/files/python/mxODBC.html

ASPN Recipe
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/144183


Pymssql seemed like the best choice. The ASPN Recipe I mention doesn't
look bad either, but there doesn't seem to be as many people using it
as using pymssql. I'll look a little further though.

 

[Filipe]

works for me, given your example:u'Fran\xd8a'

what does
print repr(row[1])

print in this case ?

It prints:
'Fran\xd8a'

The error I'm getting is beeing thrown when I print the value to the
console. If I just convert it to unicode all seems ok (except for not
beeing able to show it in the console, that is... .

For example, when I try this:
print unicode("Fran\xd8a", "iso-8859-1")

I get the error:
Traceback (most recent call last):
File "a.py", line 1, in ?
print unicode("Fran\xd8a", "iso-8859-1")
File "c:\Program Files\Python24\lib\encodings\cp437.py", line 18, in
encode
return codecs.charmap_encode(input,errors,encoding_map)
UnicodeEncodeError: 'charmap' codec can't encode character u'\xd8' in
position 4
: character maps to <undefined>

 

[Marc 'BlackJack' Rintsch]

The error I'm getting is beeing thrown when I print the value to the
console. If I just convert it to unicode all seems ok (except for not
beeing able to show it in the console, that is... .

For example, when I try this:
print unicode("Fran\xd8a", "iso-8859-1")

I get the error:
Traceback (most recent call last):
File "a.py", line 1, in ?
print unicode("Fran\xd8a", "iso-8859-1")
File "c:\Program Files\Python24\lib\encodings\cp437.py", line 18, in
encode
return codecs.charmap_encode(input,errors,encoding_map)
UnicodeEncodeError: 'charmap' codec can't encode character u'\xd8' in
position 4
: character maps to <undefined>

The `unicode()` call doesn't fail here but the ``print`` because printing
unicode strings means they have to be encoded into a byte string again.
And whatever encoding the target of the print (your console) uses, it
does not contain the unicode character u'\xd8'. From the traceback it
seems your terminal uses `cp437` as encoding.

As you can see here: http://www.wordiq.com/definition/CP437 there's no Ø
in that character set.

Ciao,
Marc 'BlackJack' Rintsch

 

[Frank Millman]

Hi,

I've done some searching and settled for pymssql, but it's not too late
to change yet.
I've found these options to connect to a MSSqlServer database:

Pymssql
http://pymssql.sourceforge.net/

ADODB for Python (windows only)
http://phplens.com/lens/adodb/adodb-py-docs.htm

SQLServer for Python (discontinued?)
http://www.object-craft.com.au/projects/mssql/

mxODBC (commercial license)
http://www.egenix.com/files/python/mxODBC.html

ASPN Recipe
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/144183

You did not mention the odbc module from Mark Hammond's win32
extensions. This is what I use, and it works for me. I believe it is
not 100% DB-API 2.0 compliant, but I have not had any problems.

I have not tried connecting to the database from a Linux box (or from
another Windows box, for that matter). I don't know if there are any
implications there.

Frank Millman

 

[=?ISO-8859-1?Q?=22Martin_v=2E_L=F6wis=22?=]

Also, it appears that DB-Library (the API used by pymssql) always
returns CP_ACP characters (unless ANSI-to-OEM conversion is enabled);
so the "right" encoding to use is "mbcs".

do you mean using something like the following line?
term = unicode(row[1], "mbcs")
Correct.

What do you mean by "ANSI-to-OEM conversion is enabled"? (sorry, I'm
quite a newbie to python)

It's an SQL server thing more than a Python thing. See AutoAnsiToOem
in

http://support.microsoft.com/default.aspx?scid=KB;EN-US;199819

Regards,
Martin

 

[Filipe]

You did not mention the odbc module from Mark Hammond's win32
extensions. This is what I use, and it works for me. I believe it is
not 100% DB-API 2.0 compliant, but I have not had any problems.

I have not tried connecting to the database from a Linux box (or from
another Windows box, for that matter). I don't know if there are any
implications there.

According to sourceforge's project page
(https://sourceforge.net/projects/pywin32/) it seems to only work on
windows.

There's also adodbapi (http://adodbapi.sourceforge.net/), that also
depends on PyWin32, but it would be very handy if I could run this code
on a linux box, and with these libs I wouldn't be able to. Still,
options are always good to have around

 

[Filipe]

The `unicode()` call doesn't fail here but the ``print`` because printing
unicode strings means they have to be encoded into a byte string again.
And whatever encoding the target of the print (your console) uses, it
does not contain the unicode character u'\xd8'. From the traceback it
seems your terminal uses `cp437` as encoding.

As you can see here: http://www.wordiq.com/definition/CP437 there's no Ø
in that character set.

somethings are much, much, clearer to me now. thanks!

For future reference, these links may also help:
http://www.jorendorff.com/articles/unicode/python.html
http://www.thescripts.com/forum/thread23314.html

I've changed my windows console copdepage to latin1 and the following
prints are now outputting "França", as expected:
print unicode("Fran\x87a", "cp850").encode("iso-8859-1")
print unicode("Fran\xe7a", "iso-8859-1").encode("iso-8859-1")

However, I don't yet fully understand what's happening with Pymssql.
The encoding I expected to be receiving from MSSqlServer was cp850 (the
column in question uses the collation SQL_Latin1_General_CP850_CS_AS),
but it doesn't seem to be what the query is returning. I tried
converting to a unicode string from a few different encodings, but none
of them seems to be the right one. For example, for cp850, using a
latin1 console:

--------------------------------------------------------
term = unicode(row[1], "cp850")
print repr(term)
print term

---- output -------------------------------------------
u'Fran\xcfa'
FranÏa
--------------------------------------------------------


And for iso-8859-1 (also got the same result for mbcs):
--------------------------------------------------------
term = unicode(row[1], "iso-8859-1")
print repr(term)
print term

---- output -------------------------------------------
u'Fran\xd8a'
FranØa

 

[Filipe]

See AutoAnsiToOem in
http://support.microsoft.com/default.aspx?scid=KB;EN-US;199819

I checked the registry key
"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Client\DB-Lib", and
verified AutoAnsiToOem was 'ON'.

I also tried assuming mbcs as the encoding but didn't got very far
(please see my other post).

 

[=?ISO-8859-1?Q?=22Martin_v=2E_L=F6wis=22?=]

---- output -------------------------------------------
u'Fran\xd8a'
FranØa

I think the data in your database is already wrong. Are you
sure the value in question is really "França" in the database?

Regards,
Martin

 

[Filipe]

I think the data in your database is already wrong. Are you
sure the value in question is really "França" in the database?

yes, I'm pretty sure. There's an application that was built to run on
top of this database and it correctly reads as writes data to the DB. I
also used SqlServer's Query Analyzer to select the data and it
displayed fine.

I've done some more tests and I think I'm very close to finding what
the problem is. The tests I had done before were executed from the
windows command line. I tried printing the following (row[1] is a value
I selected from the database) in two distinct environments, from within
an IDE (Pyscripter) and from the command line:

import sys
import locale
print getattr(sys.stdout,'encoding',None)
print locale.getdefaultlocale()[1]
print sys.getdefaultencoding()
term = "Fran\x87a"
print repr(term)
term = row[1]
print repr(term)

output I got in Pyscripter's interpreter window:
None
cp1252
ascii
'Fran\x87a'
'Fran\x87a'

output I got in the command line:
cp1252
cp1252
ascii
'Fran\x87a'
'Fran\xd8a'

I'd expect "print" to behave differently according with the console's
encoding, but does this mean this happens with repr() too?
in which way?

thanks,
Filipe

 

[=?ISO-8859-1?Q?=22Martin_v=2E_L=F6wis=22?=]

term = row[1]
print repr(term)

output I got in Pyscripter's interpreter window:
'Fran\x87a'

output I got in the command line:
'Fran\xd8a'

I'd expect "print" to behave differently according with the console's
encoding, but does this mean this happens with repr() too?

repr always generates ASCII bytes. They are not effected by the
console's encoding. If you get different output, it really means
that the values are different (check ord(row[1][4]) to be sure)

What is the precise sequence of statements that you used to
set the "row" variable?

Regards,
Martin

 

[Filipe]

term = row[1]
print repr(term)

output I got in Pyscripter's interpreter window:
'Fran\x87a'

output I got in the command line:
'Fran\xd8a'

I'd expect "print" to behave differently according with the console's
encoding, but does this mean this happens with repr() too?

repr always generates ASCII bytes. They are not effected by the
console's encoding. If you get different output, it really means
that the values are different (check ord(row[1][4]) to be sure)

They do, in fact, output different values. The value outputed by
pyscripter was "135" (x87) while the value outputed in the command line
was "216" (xd8). I can't understand why though, because the script
being run is precisely the same on both environments.

What is the precise sequence of statements that you used to
set the "row" variable?

The complete script follows:
-----------------------------------------------------------------------
import sys
import locale
print getattr(sys.stdout,'encoding',None)
print locale.getdefaultlocale()[1]
print sys.getdefaultencoding()

import pymssql
mssqlConnection =
pymssql.connect(host='localhost',user='sa',password='password',database='TestDB')
cur = mssqlConnection.cursor()
query="Select ID, Term from TestTable where ID = 204;"
cur.execute(query)
row = cur.fetchone()
results = []
while row is not None:
term = unicode(row[1], "cp850")
print ord(row[1][4])
print ord(term[4])
print term
results.append(term)
row = cur.fetchone()
cur.close()
mssqlConnection.close()
print results
-----------------------------------------------------------------------


The values outputed were, in pyscripter:
None
cp1252
ascii
135
231
França
[uFran\xe7a']

and in the command line
cp850
cp1252
ascii
216
207
FranÏa
[u'Fran\xcfa']

regards,
Filipe

 

[=?ISO-8859-1?Q?=22Martin_v=2E_L=F6wis=22?=]

They do, in fact, output different values. The value outputed by
pyscripter was "135" (x87) while the value outputed in the command line
was "216" (xd8). I can't understand why though, because the script
being run is precisely the same on both environments.

That's indeed surprising, and doesn't really increase trust into
pymssql.

If we look at the values of

print ord(row[1][4])

(where row is the actual data read from the database)

we get

The values outputed were, in pyscripter:
135

Here, 135==0x87 really is LATIN SMALL LETTER C WITH CEDILLA in
code page 850.

and in the command line
216

216==0xd8 is not LATIN SMALL LETTER C WITH CEDILLA in any
encode I know, so it appears that this value is bogus.
One would have to ask the authors of pymssql, or Microsoft,
why that happens; alternatively, you have to run pymssql
in a debugger to find out yourself.

Regards,
Martin

 

[Filipe]

Hi Martin,

One would have to ask the authors of pymssql, or Microsoft,
why that happens; alternatively, you have to run pymssql
in a debugger to find out yourself.

Tried running pymssql in a debugger, but I felt a bit lost. There are
too many things I would need to understand about pymssql first.

Meanwhile, I got to some very interesting conclusions. Remember the
"ANSI-to-OEM conversion" option you mentioned before? I began reading
some docs about it and this description turned up:

"The ANSI to OEM conversion translates data coming back from SQL Server
into the local code page used by your client."

which seemed exactly what I don't want.. so I turned it to "OFF" (by
using the registry key
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Client\DB-Lib\AutoAnsiToOem)
and everything started working the way I was originally expecting!

I think that the best way to actually solve this will be to override
AutoAnsiToOem (instead of using the registry setting) from within
pymssql, or find a way to specify what the "local code page" should be.
If not, I will have to have the pain of verifying this setting in every
system where the code I'm developing will be deployed. Which reminds
me... that this setting doesn't exist on non-windows environments (ie,
no registry on Linux) so I'm not sure how will it all work there.
Anyone with experience in using DB-Library that can confirm how it
works (namely, on linux)?
(but perhaps this is outside the scope of this newsgroup.. )

I got in touch with Andrzej Kukula, the current developer of pymssql,
who has also been very helpful, and knows what we've been discussing
over here.


thanks for all the help,
Filipe

 

[Dennis Lee Bieber]

system where the code I'm developing will be deployed. Which reminds
me... that this setting doesn't exist on non-windows environments (ie,
no registry on Linux) so I'm not sure how will it all work there.

The setting most likely has to be made on the machine running the
server -- and M$ SQL Server doesn't exist on Linux either <G>

If the conversion was being done by some client library on Windows,
then again, since that library probably doesn't exist on Linux, the
conversion probably is not done.

All conjecture...

--
Wulfraed Dennis Lee Bieber KD6MOG
(e-mail address removed) (e-mail address removed)
HTTP://wlfraed.home.netcom.com/
(Bestiaria Support Staff: (e-mail address removed))
HTTP://www.bestiaria.com/