Since we represent sequences as both strings and as lists of length-one strings, it is useful to be able to convert between the two forms. We convert lists to strings using the string.join procedure, which requires the string library.

>>> import string
>>> string.join(['A', 'G', 'C', 'G', 'C', 'A', 'A', 'U', 'G'], '')
'AGCGCAAUG'

Note that we include a second parameter to string.join, the empty string, ''. The reason for including the empty string is left as an exercise for the reader. See also: * Converting strings to lists * Converting values to representative strings