you'd grab a blob the same way you'd grab a text data type- the only difference being the data you insert. for example, make a string of letters only, insert it into both a blob and a text data type- you can get the data out exactly as is either way , however if you attempt to put binary data into a text data type, it gets corrupted (char types will pad data with spaces to fill out the length specifier, varchar will not pad, but *will* truncate trailing spaces, as will text , and in binary data- trailing spaces are critical - they are a binary character, and the alteration of a single byte in a binary file will render it useless) - it's much like taking a compiled C binary and trying to read it in a text editor - you get a long string of incomprehensible characters - putting such data in a text field in mysql would render the code un-executable, however Blob fields dont care about spaces either leading or trailing- it just stores *precisely* what you give it to store.
Ideally, if you think your data will exceed 255 characters in any given data type and it will be alphanumeric, non-binary (say, a text file) you would use TEXT field type, if you were gonna do something like store a JPG image , or even a compiled binary (cant imagine why) you would use BLOB field. Most of this information is readily available at the mysql manual, and as far as I know, Python could care less what database type you are using, it can get data from mysql as binary or integer or string or float, whatever you specify it to be.. I know that with php (my primary language, still learning python) data types are automatically converted, and with my limited work to date with python/mysql (using both python-mysqldb and the ADOdb abstraction layer for python) I have had no issues with handling data - when I get an integer from mysql that is of type integer, the value I get in python is also integer.. One thing I have been trying to research/find out is a de-cryption algorithm using our known key, to reverse mysql's own des_encrypt function - we have data stored in a mysql 4.0 table that uses that function, which is not supported in mysql 4.1 and 5 , preventing us from upgrading that one machine, and Ive been trying to find a way to match the DES3 encryption algorithm that mysql uses, (with our known key/seed of course) with little luck so far .. but in all my work, Ive never noticed any problem in handling data types- but then I read the mysql manual pretty throughly, and in my work (extremely high traffic production websites) , MySQL optimization and understanding is critical.. so maybe something seems trivially simple and obvious to me, that may actually need some explanation ? In short, whether I am working with blob or text, I would query teh table and properly type cast the variable or object to the data type I am extracting (if I know data is binary, I get it as a raw string, for example, if I know data is like an image or a compiled binary file, I would handle it as such, rather than making python process it - the object would just contain a reference to the location of the data which was extracted in the mysql query...) but then again, I do very little work with binary, and dont store files or images to a database in the first place.. :) in case I misunderstood your question- (it could also be read as how you extract the data itself from the mysql array result set) - that depends heavily on the type of query and method of fetching data, but as far as I know, you can just fetch a single piece of data from mysql as a single object, and assign it a reference... but that depends heavily on how you structure your query and has more to do with mysql than with python itself :) Bri! Adam Cripps wrote: > On 3/17/06, Brian Gustin <[EMAIL PROTECTED]> wrote: > >>if the data is not binary, you can use TEXT type - accepts all readable >>characters and data, BLOB type is more for binary data storage, and >>MYSQL's Varchar type only stores up to 255 characters. (65,536 bits, or >>64Kbits) >> >>If you are storing Binary data (DES-3 encrypted data, or image data, for >>example (a silly idea, IMHO, but some people store image data in >>databases), then you would use BLOB, but I prefer to use TEXT type for >>plain ol' storage of text or characters (say an html page or template, >>etc) rather than the binary BLOB type, although BLOB would be a space >>savings if the data will be quite large, and you will have many rows) >> >>HTH >>Bri! >> > > > Thanks - this makes sense. I will convert the table to text and see > how I get on. > > However, there is still a learning point that might be missed here - > how does Python grab BLOB data-types, and how do you manipulate them? > If it were a file, would you just be able to grab the file without the > array? > > Adam > > -- > http://www.monkeez.org > PGP key: 0x7111B833 > > !DSPAM:441be3c3320518690210016! > > _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
