Mercurial > cpython-lru_cache-weakref
diff Python/bltinmodule.c @ 23305:ef6e31f0cee1 legacy-trunk
builtin_zip(): Take a good guess at how big the result list will be,
and allocate it in one gulp.
This isn't a bugfix, it's just a minor optimization that may or may not
pay off.
| author | Tim Peters <tim.peters@gmail.com> |
|---|---|
| date | Mon, 29 Apr 2002 21:27:32 +0000 |
| parents | 6fa76b4e59fe |
| children | 642a453e7a2e |
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--- a/Python/bltinmodule.c Mon Apr 29 17:28:43 2002 +0000 +++ b/Python/bltinmodule.c Mon Apr 29 21:27:32 2002 +0000 @@ -381,7 +381,7 @@ int supplied_flags = 0; PyCompilerFlags cf; - if (!PyArg_ParseTuple(args, "sss|ii:compile", &str, &filename, + if (!PyArg_ParseTuple(args, "sss|ii:compile", &str, &filename, &startstr, &supplied_flags, &dont_inherit)) return NULL; @@ -1128,7 +1128,7 @@ v = args; else if (!PyArg_ParseTuple(args, "O:min/max", &v)) return NULL; - + it = PyObject_GetIter(v); if (it == NULL) return NULL; @@ -1704,9 +1704,10 @@ builtin_zip(PyObject *self, PyObject *args) { PyObject *ret; - int itemsize = PySequence_Length(args); + const int itemsize = PySequence_Length(args); int i; PyObject *itlist; /* tuple of iterators */ + int len; /* guess at result length */ if (itemsize < 1) { PyErr_SetString(PyExc_TypeError, @@ -1716,8 +1717,21 @@ /* args must be a tuple */ assert(PyTuple_Check(args)); + /* Guess at result length: the shortest of the input lengths. */ + len = -1; /* unknown */ + for (i = 0; i < itemsize; ++i) { + PyObject *item = PyTuple_GET_ITEM(args, i); + int thislen = PySequence_Length(item); + if (thislen < 0) + PyErr_Clear(); + else if (len < 0 || thislen < len) + len = thislen; + } + /* allocate result list */ - if ((ret = PyList_New(0)) == NULL) + if (len < 0) + len = 10; /* arbitrary */ + if ((ret = PyList_New(len)) == NULL) return NULL; /* obtain iterators */ @@ -1738,14 +1752,14 @@ } /* build result into ret list */ - for (;;) { - int status; + for (i = 0; ; ++i) { + int j; PyObject *next = PyTuple_New(itemsize); if (!next) goto Fail_ret_itlist; - for (i = 0; i < itemsize; i++) { - PyObject *it = PyTuple_GET_ITEM(itlist, i); + for (j = 0; j < itemsize; j++) { + PyObject *it = PyTuple_GET_ITEM(itlist, j); PyObject *item = PyIter_Next(it); if (!item) { if (PyErr_Occurred()) { @@ -1754,17 +1768,30 @@ } Py_DECREF(next); Py_DECREF(itlist); - return ret; + goto Done; } - PyTuple_SET_ITEM(next, i, item); + PyTuple_SET_ITEM(next, j, item); } - status = PyList_Append(ret, next); - Py_DECREF(next); - if (status < 0) - goto Fail_ret_itlist; + if (i < len) + PyList_SET_ITEM(ret, i, next); + else { + int status = PyList_Append(ret, next); + Py_DECREF(next); + ++len; + if (status < 0) + goto Fail_ret_itlist; + } } +Done: + if (ret != NULL && i < len) { + /* The list is too big. */ + if (PyList_SetSlice(ret, i, len, NULL) < 0) + return NULL; + } + return ret; + Fail_ret_itlist: Py_DECREF(itlist); Fail_ret: @@ -1864,7 +1891,7 @@ SETBUILTIN("complex", &PyComplex_Type); #endif SETBUILTIN("dict", &PyDict_Type); - SETBUILTIN("enumerate", &PyEnum_Type); + SETBUILTIN("enumerate", &PyEnum_Type); SETBUILTIN("float", &PyFloat_Type); SETBUILTIN("property", &PyProperty_Type); SETBUILTIN("int", &PyInt_Type);
