[BioPython] one function, two behaivors

[Sebastian Bassi]

If I invoke "transcribe" with a RNA sequence like this:

>>> from Bio.Seq import transcribe
>>> from Bio.Seq import Seq
>>> import Bio.Alphabet
>>> rna_seq = Seq('CCGGGUU',Bio.Alphabet.IUPAC.unambiguous_rna)
>>> transcribe(rna_seq)  # Look!, I am "transcribing a RNA"
Seq('CCGGGUU', RNAAlphabet())

But I can't "transcribe" a RNA sequence if I invoke it this way:

>>> from Bio import Transcribe
>>> transcriber = Transcribe.unambiguous_transcriber
>>> transcriber.transcribe(rna_seq)

Traceback (most recent call last):
  File "<pyshell#13>", line 1, in <module>
    transcriber.transcribe(rna_seq)
  File "/usr/local/lib/python2.5/site-packages/Bio/Transcribe.py",
line 13, in transcribe
    "transcribe has the wrong DNA alphabet"
AssertionError: transcribe has the wrong DNA alphabet

The same result I get when using "translate". What is the rationale behind this?

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