String character encoding when converting data from one type/format to another

Ned Batchelder ned at nedbatchelder.com
Wed Jan 7 13:02:34 CET 2015


On 1/7/15 6:04 AM, Jacob Kruger wrote:
> I'm busy using something like pyodbc to pull data out of MS access .mdb
> files, and then generate .sql script files to execute against MySQL
> databases using MySQLdb module, but, issue is forms of characters in
> string values that don't fit inside the 0-127 range - current one seems
> to be something like \xa3, and if I pass it through ord() function, it
> comes out as character number 163.
> Now issue is, yes, could just run through the hundreds of thousands of
> characters in these resulting strings, and strip out any that are not
> within the basic 0-127 range, but, that could result in corrupting data
> - think so anyway.

That will definitely corrupt your data, since you will be discarding data.

> Anyway, issue is, for example, if I try something like
> str('\xa3').encode('utf-8') or str('\xa3').encode('ascii'), or
> str('\xa3').encode('latin7') - that last one is actually our preferred
> encoding for the MySQL database - they all just tell me they can't work
> with a character out of range.

Are you using Python 2 or Python 3? This is one area where the two are 
very different.  I suspect you are on Python 2, in which case these all 
fail the same way because you are calling encode on a bytestring.  You 
can't encode a bytestring, you can only encode a Unicode string, so 
encode is helpfully trying to decode your bytestring first, using the 
default encoding (ascii), and '\xa3' is not an ascii character.

If that was confusing, this talk covers these fundamentals: 
http://bit.ly/unipain .

> Any thoughts on a sort of generic method/means to handle any/all
> characters that might be out of range when having pulled them out of
> something like these MS access databases?

The best thing is to know what encoding was used to produce these byte 
values.  Then you can manipulate them as Unicode if you need to.  The 
second best thing is to simply pass them through as bytes.

> Another side note is for binary values that might store binary values, I
> use something like the following to generate hex-based strings that work
> alright when then inserting said same binary values into longblob
> fields, but, don't think this would really help for what are really just
> most likely badly chosen copy/pasted strings from documents, with
> strange encoding, or something:
> #sample code line for binary encoding into string output
> s_values += "0x" + str(l_data[J][I]).encode("hex").replace("\\", "\\\\")
> + ", "
> TIA
>
> Jacob Kruger
> Blind Biker
> Skype: BlindZA
> "Roger Wilco wants to welcome you...to the space janitor's closet..."
>
>


-- 
Ned Batchelder, http://nedbatchelder.com




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