new method for string objects

[Andrew Dalke]

Fredrik Lundh wrote:
>assuming that "string value" means the "raw contents of the
>sequence object", you should use a buffer objects instead.
>you can use the 'buffer' builtin to turn most sequence objects
>into buffers:


I had never heard of 'buffer' before.  I looked into it a bit.
It seems like it only works with C based structures as there's
no way to get the buffer of an object.

I have a "Seq" class which looks like:

class Seq:
  def __init__(self, letters, alphabet = Alphabet.generic_alphabet):
    assert type(letters) == type("")  # input must be a string
    self.letters = letters
    self.alphabet = alphabet
  def tostring(self):
    return self.letters

and I have a translation function which looks like:

def translate(seq, table = TranslationTable.standard_table):
  s = seq  # or "s = seq.tostring()"
  letters = []
  for i in range(0, len(s), 3):
    letters.append(table[s[i:i+3]])
  return Seq(string.join(letters, table.forward_alphabet))

If the input is a string or an array.array, then I can
replace the "s = seq" with your buffer suggestion.

  s = buffer(seq)

However, if the sequence is a Seq object, then buffer won't
work.  (I added a __getattr__ to the Seq object to see if
the buffer() gets an attribute from an instance; it doesn't.)

On the other hand, if strings have a "tostring" method, then I
can always use:

  s = seq.tostring()

                    Andrew Dalke
                    dalke at acm.org