[Patches] string.translate behaviour
Peter Schneider-Kamp
peter@schneider-kamp.de
Sun, 28 May 2000 11:48:11 +0200
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Problem:
The string.translate() function has an unpleasant interface, requiring a
256-character string containing a translation table.
string.maketrans() was subsequently added as a helper function to make
the job easier, but string.translate() should really have an
interface like maketrans: (fromchars, tochars [, deletechars])
AMK says: I later proposed a solution that would let us keep
string.translate, and would behave naturally, yet doesn't seem likely to
break any code. string.translate would have a signature (fromchars,
tochars [, deletechars]). If len(fromchars)!=256, it must be the
new style; otherwise it must be the old style. The only ambiguous is if
len(fromchars)==len(tochars)==256; is it a new-style call
that's doing a complete permutation, or is it an old-style call with a
256-char list of characters to delete. Case II seems unlikely to
occur in practice, so we'll assume case I and resolve the ambiguity that
way.
AMK will implement this one spare weekend.
Edit this entry / Log info / Last changed on Wed Jul 22 09:26:56 1998 by
A.M. Kuchling
Solution:
I still think this is a good idea and so I have implemented
this behaviour. It does not make the code cleaner, but it's sure
a nice feature to have.
patch attached as plaintext context diff
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Peter Schneider-Kamp ++47-7388-7331
Herman Krags veg 51-11 mailto:peter@schneider-kamp.de
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diff -c --recursive python/dist/src/Objects/stringobject.c python-mod/dist/src/Objects/stringobject.c
*** python/dist/src/Objects/stringobject.c Mon May 8 16:08:05 2000
--- python-mod/dist/src/Objects/stringobject.c Mon May 22 10:33:26 2000
***************
*** 1293,1308 ****
int inlen, tablen, dellen = 0;
PyObject *result;
int trans_table[256];
! PyObject *tableobj, *delobj = NULL;
! if (!PyArg_ParseTuple(args, "O|O:translate",
! &tableobj, &delobj))
return NULL;
if (PyString_Check(tableobj)) {
table1 = PyString_AS_STRING(tableobj);
! tablen = PyString_GET_SIZE(tableobj);
! }
else if (PyUnicode_Check(tableobj)) {
/* Unicode .translate() does not support the deletechars
parameter; instead a mapping to None will cause characters
--- 1293,1309 ----
int inlen, tablen, dellen = 0;
PyObject *result;
int trans_table[256];
! char new_table[256];
! PyObject *tableobj, *delobj = NULL, *delchars = NULL;
! if (!PyArg_ParseTuple(args, "O|OO:translate",
! &tableobj, &delobj, &delchars))
return NULL;
if (PyString_Check(tableobj)) {
table1 = PyString_AS_STRING(tableobj);
! tablen = PyString_GET_SIZE(tableobj);
! }
else if (PyUnicode_Check(tableobj)) {
/* Unicode .translate() does not support the deletechars
parameter; instead a mapping to None will cause characters
***************
*** 1329,1344 ****
}
else if (PyObject_AsCharBuffer(delobj, &del_table, &dellen))
return NULL;
-
- if (tablen != 256) {
- PyErr_SetString(PyExc_ValueError,
- "translation table must be 256 characters long");
- return NULL;
- }
}
else {
del_table = NULL;
dellen = 0;
}
table = table1;
--- 1330,1374 ----
}
else if (PyObject_AsCharBuffer(delobj, &del_table, &dellen))
return NULL;
}
else {
del_table = NULL;
dellen = 0;
+ if (tablen != 256) {
+ PyErr_SetString(PyExc_ValueError,
+ "translation table must be a 256 char string.");
+ return NULL;
+ }
+ }
+
+ if ((delobj != NULL) && ((tablen != 256) || (dellen == 256))) {
+ if (tablen != dellen) {
+ PyErr_SetString(PyExc_ValueError,
+ "arguments fromchar and tochar must match in size");
+ return NULL;
+ }
+ for (i = 0; i < 256; i++)
+ new_table[i] = (unsigned char)i;
+ for (i = 0; i < tablen; i++)
+ new_table[table1[i]] = del_table[i];
+ table1 = new_table;
+ if (delchars != NULL) {
+ if (PyString_Check(delchars)) {
+ del_table = PyString_AS_STRING(delchars);
+ dellen = PyString_GET_SIZE(delchars);
+ }
+ else if (PyUnicode_Check(delchars)) {
+ PyErr_SetString(PyExc_TypeError,
+ "deletions are implemented differently for unicode");
+ return NULL;
+ }
+ else if (PyObject_AsCharBuffer(delchars, &del_table, &dellen))
+ return NULL;
+ }
+ else {
+ del_table = NULL;
+ dellen = 0;
+ }
}
table = table1;
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