In Python you can use the array module to quickly convert ASCII values to a string and back again.

>>> import array
>>> array.array('B', [97, 98, 99]).tostring()
'abc'
>>> array.array('B', 'abc').tolist()
[97, 98, 99]

For more information, read Python Patterns - An Optimization Anecdote.

If you need to convert a TEXT column to a BYTEA column, you can use a cast expression to do the work:

ALTER TABLE mytable ALTER COLUMN col TYPE bytea USING
  decode(replace(col, '\\', '\\\\'), 'escape');

Note that altering the column type of a column is only supported beginning with PostgreSQL version 8.0. For more information, see the manual.

If you find yourself needing to drop the case on the entire contents of a file, you can try this:

$ dd if=original of=filtered conv=lcase

-or-

$ tr '[A-Z]' '[a-z]' < original > filtered