I want to write a python script that populates a database with some information. One of the columns in my table is a BLOB that I would like to save a file to for each entry.
How can I read the file (binary) and insert it into the DB using python? Likewise, how can I retrieve it and write that file back to some arbitrary location on the hard drive?
You can insert and read BLOBs from a DB like every other column type. From the database API's view there is nothing special about BLOBs.
thedata = open('thefile', 'rb').read()
sql = "INSERT INTO sometable (theblobcolumn) VALUES (%s)"
cursor.execute(sql, (thedata,))
That code of course works as written only if your table has just the BLOB column and what you want to do is INSERT, but of course you could easily tweak it to add more columns, use UPDATE instead of INSERT, or whatever it is that you exactly need to do.
I'm also assuming your file is binary rather than text, etc; again, if my guesses are incorrect it's easy for you to tweak the above code accordingly.
Some kind of SELECT on cursor.execute, then some kind of fetching from the cursor, is how you
retrieve BLOB data, exactly like you retrieve any other kind of data.