diff options
| -rw-r--r-- | Doc/howto/doanddont.tex | 14 | ||||
| -rw-r--r-- | Doc/lib/libfuncs.tex | 15 | ||||
| -rw-r--r-- | Doc/lib/libfunctools.tex | 13 | ||||
| -rw-r--r-- | Doc/tut/tut.tex | 42 | ||||
| -rw-r--r-- | Lib/functools.py | 2 | ||||
| -rw-r--r-- | Lib/test/test_functools.py | 71 | ||||
| -rw-r--r-- | Misc/Vim/python.vim | 2 | ||||
| -rw-r--r-- | Misc/cheatsheet | 7 | ||||
| -rw-r--r-- | Misc/python-mode.el | 2 | ||||
| -rw-r--r-- | Modules/_functoolsmodule.c | 76 | ||||
| -rw-r--r-- | Python/Python-ast.c | 2 |
11 files changed, 168 insertions, 78 deletions
diff --git a/Doc/howto/doanddont.tex b/Doc/howto/doanddont.tex index a105ca1fce..df3ca346a4 100644 --- a/Doc/howto/doanddont.tex +++ b/Doc/howto/doanddont.tex @@ -289,19 +289,7 @@ There are also many useful builtin functions people seem not to be aware of for some reason: \function{min()} and \function{max()} can find the minimum/maximum of any sequence with comparable semantics, for example, yet many people write their own -\function{max()}/\function{min()}. Another highly useful function is -\function{reduce()}. A classical use of \function{reduce()} -is something like - -\begin{verbatim} -import sys, operator -nums = map(float, sys.argv[1:]) -print reduce(operator.add, nums)/len(nums) -\end{verbatim} - -This cute little script prints the average of all numbers given on the -command line. The \function{reduce()} adds up all the numbers, and -the rest is just some pre- and postprocessing. +\function{max()}/\function{min()}. On the same note, note that \function{float()}, \function{int()} and \function{long()} all accept arguments of type string, and so are diff --git a/Doc/lib/libfuncs.tex b/Doc/lib/libfuncs.tex index 65b0bf5381..c9e35b57e7 100644 --- a/Doc/lib/libfuncs.tex +++ b/Doc/lib/libfuncs.tex @@ -836,19 +836,6 @@ class Parrot(object): \end{verbatim} \end{funcdesc} -\begin{funcdesc}{reduce}{function, sequence\optional{, initializer}} - Apply \var{function} of two arguments cumulatively to the items of - \var{sequence}, from left to right, so as to reduce the sequence to - a single value. For example, \code{reduce(lambda x, y: x+y, [1, 2, - 3, 4, 5])} calculates \code{((((1+2)+3)+4)+5)}. The left argument, - \var{x}, is the accumulated value and the right argument, \var{y}, - is the update value from the \var{sequence}. If the optional - \var{initializer} is present, it is placed before the items of the - sequence in the calculation, and serves as a default when the - sequence is empty. If \var{initializer} is not given and - \var{sequence} contains only one item, the first item is returned. -\end{funcdesc} - \begin{funcdesc}{reload}{module} Reload a previously imported \var{module}. The argument must be a module object, so it must have been successfully @@ -1058,8 +1045,6 @@ class C: The \var{sequence}'s items are normally numbers, and are not allowed to be strings. The fast, correct way to concatenate sequence of strings is by calling \code{''.join(\var{sequence})}. - Note that \code{sum(range(\var{n}), \var{m})} is equivalent to - \code{reduce(operator.add, range(\var{n}), \var{m})} \versionadded{2.3} \end{funcdesc} diff --git a/Doc/lib/libfunctools.tex b/Doc/lib/libfunctools.tex index 33a6f52964..034143a50c 100644 --- a/Doc/lib/libfunctools.tex +++ b/Doc/lib/libfunctools.tex @@ -51,6 +51,19 @@ two: \end{verbatim} \end{funcdesc} +\begin{funcdesc}{reduce}{function, sequence\optional{, initializer}} + Apply \var{function} of two arguments cumulatively to the items of + \var{sequence}, from left to right, so as to reduce the sequence to + a single value. For example, \code{reduce(lambda x, y: x+y, [1, 2, + 3, 4, 5])} calculates \code{((((1+2)+3)+4)+5)}. The left argument, + \var{x}, is the accumulated value and the right argument, \var{y}, + is the update value from the \var{sequence}. If the optional + \var{initializer} is present, it is placed before the items of the + sequence in the calculation, and serves as a default when the + sequence is empty. If \var{initializer} is not given and + \var{sequence} contains only one item, the first item is returned. +\end{funcdesc} + \begin{funcdesc}{update_wrapper} {wrapper, wrapped\optional{, assigned}\optional{, updated}} Update a wrapper function to look like the wrapped function. The optional diff --git a/Doc/tut/tut.tex b/Doc/tut/tut.tex index 1b08a8e3a8..6f6fe6ffaa 100644 --- a/Doc/tut/tut.tex +++ b/Doc/tut/tut.tex @@ -1893,8 +1893,8 @@ use \method{pop()} with \code{0} as the index. For example: \subsection{Functional Programming Tools \label{functional}} -There are three built-in functions that are very useful when used with -lists: \function{filter()}, \function{map()}, and \function{reduce()}. +There are two built-in functions that are very useful when used with +lists: \function{filter()} and \function{map()}. \samp{filter(\var{function}, \var{sequence})} returns a sequence consisting of those items from the @@ -1934,42 +1934,6 @@ is shorter than another). For example: >>> map(add, seq, seq) [0, 2, 4, 6, 8, 10, 12, 14] \end{verbatim} - -\samp{reduce(\var{function}, \var{sequence})} returns a single value -constructed by calling the binary function \var{function} on the first two -items of the sequence, then on the result and the next item, and so -on. For example, to compute the sum of the numbers 1 through 10: - -\begin{verbatim} ->>> def add(x,y): return x+y -... ->>> reduce(add, range(1, 11)) -55 -\end{verbatim} - -If there's only one item in the sequence, its value is returned; if -the sequence is empty, an exception is raised. - -A third argument can be passed to indicate the starting value. In this -case the starting value is returned for an empty sequence, and the -function is first applied to the starting value and the first sequence -item, then to the result and the next item, and so on. For example, - -\begin{verbatim} ->>> def sum(seq): -... def add(x,y): return x+y -... return reduce(add, seq, 0) -... ->>> sum(range(1, 11)) -55 ->>> sum([]) -0 -\end{verbatim} - -Don't use this example's definition of \function{sum()}: since summing -numbers is such a common need, a built-in function -\code{sum(\var{sequence})} is already provided, and works exactly like -this. \versionadded{2.3} \subsection{List Comprehensions} @@ -2739,7 +2703,7 @@ standard module \module{__builtin__}\refbimodindex{__builtin__}: 'id', 'int', 'intern', 'isinstance', 'issubclass', 'iter', 'len', 'license', 'list', 'locals', 'long', 'map', 'max', 'min', 'object', 'oct', 'open', 'ord', 'pow', 'property', 'quit', 'range', - 'reduce', 'reload', 'repr', 'reversed', 'round', 'set', + 'reload', 'repr', 'reversed', 'round', 'set', 'setattr', 'slice', 'sorted', 'staticmethod', 'str', 'sum', 'super', 'tuple', 'type', 'unichr', 'unicode', 'vars', 'xrange', 'zip'] \end{verbatim} diff --git a/Lib/functools.py b/Lib/functools.py index 8783f08488..12a527e360 100644 --- a/Lib/functools.py +++ b/Lib/functools.py @@ -7,7 +7,7 @@ # Copyright (C) 2006 Python Software Foundation. # See C source code for _functools credits/copyright -from _functools import partial +from _functools import partial, reduce # update_wrapper() and wraps() are tools to help write # wrapper functions that can handle naive introspection diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py index 8dc185b721..01d6cd29e8 100644 --- a/Lib/test/test_functools.py +++ b/Lib/test/test_functools.py @@ -259,6 +259,74 @@ class TestWraps(TestUpdateWrapper): self.assertEqual(wrapper.attr, 'This is a different test') self.assertEqual(wrapper.dict_attr, f.dict_attr) +class TestReduce(unittest.TestCase): + func = functools.reduce + + def test_reduce(self): + class Squares: + def __init__(self, max): + self.max = max + self.sofar = [] + + def __len__(self): + return len(self.sofar) + + def __getitem__(self, i): + if not 0 <= i < self.max: raise IndexError + n = len(self.sofar) + while n <= i: + self.sofar.append(n*n) + n += 1 + return self.sofar[i] + + self.assertEqual(self.func(lambda x, y: x+y, ['a', 'b', 'c'], ''), 'abc') + self.assertEqual( + self.func(lambda x, y: x+y, [['a', 'c'], [], ['d', 'w']], []), + ['a','c','d','w'] + ) + self.assertEqual(self.func(lambda x, y: x*y, range(2,8), 1), 5040) + self.assertEqual( + self.func(lambda x, y: x*y, range(2,21), 1L), + 2432902008176640000L + ) + self.assertEqual(self.func(lambda x, y: x+y, Squares(10)), 285) + self.assertEqual(self.func(lambda x, y: x+y, Squares(10), 0), 285) + self.assertEqual(self.func(lambda x, y: x+y, Squares(0), 0), 0) + self.assertRaises(TypeError, self.func) + self.assertRaises(TypeError, self.func, 42, 42) + self.assertRaises(TypeError, self.func, 42, 42, 42) + self.assertEqual(self.func(42, "1"), "1") # func is never called with one item + self.assertEqual(self.func(42, "", "1"), "1") # func is never called with one item + self.assertRaises(TypeError, self.func, 42, (42, 42)) + + class BadSeq: + def __getitem__(self, index): + raise ValueError + self.assertRaises(ValueError, self.func, 42, BadSeq()) + + # Test reduce()'s use of iterators. + def test_iterator_usage(self): + class SequenceClass: + def __init__(self, n): + self.n = n + def __getitem__(self, i): + if 0 <= i < self.n: + return i + else: + raise IndexError + + from operator import add + self.assertEqual(self.func(add, SequenceClass(5)), 10) + self.assertEqual(self.func(add, SequenceClass(5), 42), 52) + self.assertRaises(TypeError, self.func, add, SequenceClass(0)) + self.assertEqual(self.func(add, SequenceClass(0), 42), 42) + self.assertEqual(self.func(add, SequenceClass(1)), 0) + self.assertEqual(self.func(add, SequenceClass(1), 42), 42) + + d = {"one": 1, "two": 2, "three": 3} + self.assertEqual(self.func(add, d), "".join(d.keys())) + + def test_main(verbose=None): @@ -268,7 +336,8 @@ def test_main(verbose=None): TestPartialSubclass, TestPythonPartial, TestUpdateWrapper, - TestWraps + TestWraps, + TestReduce ) test_support.run_unittest(*test_classes) diff --git a/Misc/Vim/python.vim b/Misc/Vim/python.vim index d83572aa35..08c54d24e8 100644 --- a/Misc/Vim/python.vim +++ b/Misc/Vim/python.vim @@ -63,7 +63,7 @@ endif if exists("python_highlight_builtins") syn keyword pythonBuiltin unichr all set abs vars int __import__ unicode - syn keyword pythonBuiltin enumerate reduce exit issubclass + syn keyword pythonBuiltin enumerate exit issubclass syn keyword pythonBuiltin divmod file Ellipsis isinstance open any syn keyword pythonBuiltin locals help filter basestring slice copyright min syn keyword pythonBuiltin super sum tuple hex execfile long id chr diff --git a/Misc/cheatsheet b/Misc/cheatsheet index 65b1400e6b..bab109a8ab 100644 --- a/Misc/cheatsheet +++ b/Misc/cheatsheet @@ -901,7 +901,7 @@ lambda [param_list]: returnedExpr -- Creates an anonymous function. returnedExpr must be an expression, not a statement (e.g., not "if xx:...", "print xxx", etc.) and thus can't contain newlines. - Used mostly for filter(), map(), reduce() functions, and GUI callbacks.. + Used mostly for filter(), map() functions, and GUI callbacks.. List comprehensions result = [expression for item1 in sequence1 [if condition1] [for item2 in sequence2 ... for itemN in sequenceN] @@ -1005,11 +1005,6 @@ property() Created a property with access controlled by functions. range(start [,end Returns list of ints from >= start and < end.With 1 arg, [, step]]) list from 0..arg-1With 2 args, list from start..end-1With 3 args, list from start up to end by step -reduce(f, list [, Applies the binary function f to the items oflist so as to -init]) reduce the list to a single value.If init given, it is - "prepended" to list. - Re-parses and re-initializes an already imported module. - Useful in interactive mode, if you want to reload amodule reload(module) after fixing it. If module was syntacticallycorrect but had an error in initialization, mustimport it one more time before calling reload(). diff --git a/Misc/python-mode.el b/Misc/python-mode.el index 1392c84d62..5f50da8add 100644 --- a/Misc/python-mode.el +++ b/Misc/python-mode.el @@ -386,7 +386,7 @@ support for features needed by `python-mode'.") "isinstance" "issubclass" "iter" "len" "license" "list" "locals" "long" "map" "max" "min" "object" "oct" "open" "ord" "pow" "property" "range" - "reduce" "reload" "repr" "round" + "reload" "repr" "round" "setattr" "slice" "staticmethod" "str" "sum" "super" "tuple" "type" "unichr" "unicode" "vars" "zip") diff --git a/Modules/_functoolsmodule.c b/Modules/_functoolsmodule.c index 7b23210617..1b363fcab4 100644 --- a/Modules/_functoolsmodule.c +++ b/Modules/_functoolsmodule.c @@ -242,12 +242,88 @@ static PyTypeObject partial_type = { }; +/* reduce (used to be a builtin) ********************************************/ + +static PyObject * +functools_reduce(PyObject *self, PyObject *args) +{ + PyObject *seq, *func, *result = NULL, *it; + + if (!PyArg_UnpackTuple(args, "reduce", 2, 3, &func, &seq, &result)) + return NULL; + if (result != NULL) + Py_INCREF(result); + + it = PyObject_GetIter(seq); + if (it == NULL) { + PyErr_SetString(PyExc_TypeError, + "reduce() arg 2 must support iteration"); + Py_XDECREF(result); + return NULL; + } + + if ((args = PyTuple_New(2)) == NULL) + goto Fail; + + for (;;) { + PyObject *op2; + + if (args->ob_refcnt > 1) { + Py_DECREF(args); + if ((args = PyTuple_New(2)) == NULL) + goto Fail; + } + + op2 = PyIter_Next(it); + if (op2 == NULL) { + if (PyErr_Occurred()) + goto Fail; + break; + } + + if (result == NULL) + result = op2; + else { + PyTuple_SetItem(args, 0, result); + PyTuple_SetItem(args, 1, op2); + if ((result = PyEval_CallObject(func, args)) == NULL) + goto Fail; + } + } + + Py_DECREF(args); + + if (result == NULL) + PyErr_SetString(PyExc_TypeError, + "reduce() of empty sequence with no initial value"); + + Py_DECREF(it); + return result; + +Fail: + Py_XDECREF(args); + Py_XDECREF(result); + Py_DECREF(it); + return NULL; +} + +PyDoc_STRVAR(functools_reduce_doc, +"reduce(function, sequence[, initial]) -> value\n\ +\n\ +Apply a function of two arguments cumulatively to the items of a sequence,\n\ +from left to right, so as to reduce the sequence to a single value.\n\ +For example, reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) calculates\n\ +((((1+2)+3)+4)+5). If initial is present, it is placed before the items\n\ +of the sequence in the calculation, and serves as a default when the\n\ +sequence is empty."); + /* module level code ********************************************************/ PyDoc_STRVAR(module_doc, "Tools that operate on functions."); static PyMethodDef module_methods[] = { + {"reduce", functools_reduce, METH_VARARGS, functools_reduce_doc}, {NULL, NULL} /* sentinel */ }; diff --git a/Python/Python-ast.c b/Python/Python-ast.c index 11f42b894c..68523e4904 100644 --- a/Python/Python-ast.c +++ b/Python/Python-ast.c @@ -3012,7 +3012,7 @@ init_ast(void) if (PyDict_SetItemString(d, "AST", (PyObject*)AST_type) < 0) return; if (PyModule_AddIntConstant(m, "PyCF_ONLY_AST", PyCF_ONLY_AST) < 0) return; - if (PyModule_AddStringConstant(m, "__version__", "45597") < 0) + if (PyModule_AddStringConstant(m, "__version__", "51600") < 0) return; if (PyDict_SetItemString(d, "mod", (PyObject*)mod_type) < 0) return; if (PyDict_SetItemString(d, "Module", (PyObject*)Module_type) < 0) |