Terry J. Reedy added the comment:
The docstring is more accurate.
">>> str.translate.__doc__
'S.translate(table) -> str\n\nReturn a copy of the string S, where all
characters have been mapped\nthrough the given translation table, which must be
a mapping of\nUnicode ordinals to Unicode ordinals, strings, or None.\nUnmapped
characters are left untouched. Characters mapped to None\nare deleted.'""
To me, even this is a bit unclear on exceptions and 'unmapped'. Based on
experiments and then reading the C source, I determined that LookupErrors mean
'unmapped' while other exceptions are passed on and terminate the translation.
"Return a copy of the string S, where all characters have been mapped through
the given translation table. When subscripted by a Unicode ordinal (integer in
range(1048576)), the table must return a Unicode ordinal, string, or None, or
else raise a LookupError. A LookupError, which includes instances of subclasses
IndexError and KeyError, indicates that the character is unmapped and should be
left untouched. Characters mapped to None are deleted."
class Table:
def __getitem__(self, key):
if key == 99: raise LookupError() #'c'
elif key == 100: return None # 'd'
elif key == 101: return 'xyz' # 'e'
else: return key+1
print('abcdef'.translate(Table()))
# bccxyzg
The current doc ends with "Note
An even more flexible approach is to create a custom character mapping codec
using the codecs module (see encodings.cp1251 for an example)."
I don't see how this is supposed to help. Encodings.cp1251 uses a string of 256
chars as a lookup table.
----------
nosy: +terry.reedy
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