Well, having variable substitution inside strings would be a useful
feature for multi-line strings (only) For single line strings, the
'%' printf operator works well, but look at this multi-line string:
"""The %d numbers of %s objects gets harder and harder to read
as the number of %s lines gets greater than about %d lines long due
to the loss of %s as you are scanning through the text.""" % \
(5, 'python', 'text', 3, 'context')
This is much better:
n = 2
language = 'python'
"""The {n} numbers of {language} objects is usually easy to read in
long strings because you can see which variable gets substituted in
a given point."""
Where inside of a long string, """ TX1 {expr} TX2 """ is equivalant
to """ TX1 """ + `expr` + """ TX2 """