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Add __asdict__() to NamedTuple and refine the docs. 

Add maxlen support to deque() and fixup docs.
Partially fix __reduce__().  The None as a third arg was no longer supported.
Still needs work on __reduce__() to handle recursive inputs.
This commit is contained in:
Raymond Hettinger 2007-10-05 02:47:07 +00:00
parent c9b7163da5
commit a7fc4b13e0
6 changed files with 228 additions and 162 deletions
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95
Doc/library/collections.rst
View File

@ -34,7 +34,7 @@ ordered dictionaries.
----------------------
.. class:: deque([iterable])
.. class:: deque([iterable[, maxlen]])
Returns a new deque object initialized left-to-right (using :meth:`append`) with
data from *iterable*. If *iterable* is not specified, the new deque is empty.
@ -51,6 +51,17 @@ ordered dictionaries.
.. versionadded:: 2.4
If *maxlen* is not specified or is *-1*, deques may grow to an
arbitrary length. Otherwise, the deque is bounded to the specified maximum
length. Once a bounded length deque is full, when new items are added, a
corresponding number of items are discarded from the opposite end. Bounded
length deques provide functionality similar to the ``tail`` filter in
Unix. They are also useful for tracking transactions and other pools of data
where only the most recent activity is of interest.
.. versionchanged:: 2.6
Added *maxlen*
Deque objects support the following methods:
@ -168,8 +179,8 @@ Example::
.. _deque-recipes:
Recipes
^^^^^^^
:class:`deque` Recipes
^^^^^^^^^^^^^^^^^^^^^^
This section shows various approaches to working with deques.
@ -186,42 +197,14 @@ To implement :class:`deque` slicing, use a similar approach applying
:meth:`rotate` to bring a target element to the left side of the deque. Remove
old entries with :meth:`popleft`, add new entries with :meth:`extend`, and then
reverse the rotation.
With minor variations on that approach, it is easy to implement Forth style
stack manipulations such as ``dup``, ``drop``, ``swap``, ``over``, ``pick``,
``rot``, and ``roll``.
A roundrobin task server can be built from a :class:`deque` using
:meth:`popleft` to select the current task and :meth:`append` to add it back to
the tasklist if the input stream is not exhausted::
>>> def roundrobin(*iterables):
... pending = deque(iter(i) for i in iterables)
... while pending:
... task = pending.popleft()
... try:
... yield task.next()
... except StopIteration:
... continue
... pending.append(task)
...
>>> for value in roundrobin('abc', 'd', 'efgh'):
... print value
a
d
e
b
f
c
g
h
Multi-pass data reduction algorithms can be succinctly expressed and efficiently
coded by extracting elements with multiple calls to :meth:`popleft`, applying
the reduction function, and calling :meth:`append` to add the result back to the
queue.
a reduction function, and calling :meth:`append` to add the result back to the
deque.
For example, building a balanced binary tree of nested lists entails reducing
two adjacent nodes into one by grouping them in a list::
@ -236,7 +219,12 @@ two adjacent nodes into one by grouping them in a list::
>>> print maketree('abcdefgh')
[[[['a', 'b'], ['c', 'd']], [['e', 'f'], ['g', 'h']]]]
Bounded length deques provide functionality similar to the ``tail`` filter
in Unix::
def tail(filename, n=10):
'Return the last n lines of a file'
return deque(open(filename), n)
.. _defaultdict-objects:
@ -376,7 +364,8 @@ they add the ability to access fields by name instead of position index.
method which lists the tuple contents in a ``name=value`` format.
The *fieldnames* are specified in a single string with each fieldname separated by
a space and/or comma. Any valid Python identifier may be used for a fieldname.
a space and/or comma. Any valid Python identifier may be used for a fieldname
except for names starting and ending with double underscores.
If *verbose* is true, will print the class definition.
@ -387,7 +376,7 @@ they add the ability to access fields by name instead of position index.
Example::
>>> Point = NamedTuple('Point', 'x y', True)
>>> Point = NamedTuple('Point', 'x y', verbose=True)
class Point(tuple):
'Point(x, y)'
__slots__ = ()
@ -396,6 +385,9 @@ Example::
return tuple.__new__(cls, (x, y))
def __repr__(self):
return 'Point(x=%r, y=%r)' % self
def __asdict__(self):
'Return a new dict mapping field names to their values'
return dict(zip(('x', 'y'), self))
def __replace__(self, field, value):
'Return a new Point object replacing one field with a new value'
return Point(**dict(zip(('x', 'y'), self) + [(field, value)]))
@ -429,10 +421,25 @@ the values::
>>> Point(*t) # the star-operator unpacks any iterable object
Point(x=11, y=22)
In addition to the methods inherited from tuples, named tuples support
an additonal method and an informational read-only attribute.
When casting a dictionary to a *NamedTuple*, use the double-star-operator::
.. method:: somenamedtuple.replace(field, value)
>>> d = {'x': 11, 'y': 22}
>>> Point(**d)
Point(x=11, y=22)
In addition to the methods inherited from tuples, named tuples support
additonal methods and a read-only attribute.
.. method:: somenamedtuple.__asdict__()
Return a new dict which maps field names to their corresponding values:
::
>>> p.__asdict__()
{'x': 11, 'y': 22}
.. method:: somenamedtuple.__replace__(field, value)
Return a new instance of the named tuple replacing the named *field* with a new *value*:
@ -447,20 +454,16 @@ an additonal method and an informational read-only attribute.
.. attribute:: somenamedtuple.__fields__
Return a tuple of strings listing the field names. This is useful for introspection,
for converting a named tuple instance to a dictionary, and for combining named tuple
types to create new named tuple types:
Return a tuple of strings listing the field names. This is useful for introspection
and for creating new named tuple types from existing named tuples.
::
>>> p.__fields__ # view the field names
>>> p.__fields__ # view the field names
('x', 'y')
>>> dict(zip(p.__fields__, p)) # convert to a dictionary
{'y': 22, 'x': 11}
>>> Color = NamedTuple('Color', 'red green blue')
>>> pixel_fields = ' '.join(Point.__fields__ + Color.__fields__) # combine fields
>>> Pixel = NamedTuple('Pixel', pixel_fields)
>>> Pixel = NamedTuple('Pixel', ' '.join(Point.__fields__ + Color.__fields__))
>>> Pixel(11, 22, 128, 255, 0)
Pixel(x=11, y=22, red=128, green=255, blue=0)'

15
Lib/collections.py
View File

@ -18,19 +18,21 @@ def NamedTuple(typename, s, verbose=False):
(11, 22)
>>> p.x + p.y # fields also accessable by name
33
>>> p # readable __repr__ with name=value style
>>> d = p.__asdict__() # convert to a dictionary
>>> d['x']
11
>>> Point(**d) # convert from a dictionary
Point(x=11, y=22)
>>> p.__replace__('x', 100) # __replace__() is like str.replace() but targets a named field
Point(x=100, y=22)
>>> d = dict(zip(p.__fields__, p)) # use __fields__ to make a dictionary
>>> d['x']
11
"""
field_names = tuple(s.replace(',', ' ').split()) # names separated by spaces and/or commas
if not ''.join((typename,) + field_names).replace('_', '').isalnum():
raise ValueError('Type names and field names can only contain alphanumeric characters and underscores')
if any(name.startswith('__') and name.endswith('__') for name in field_names):
raise ValueError('Field names cannot start and end with double underscores')
argtxt = repr(field_names).replace("'", "")[1:-1] # tuple repr without parens or quotes
reprtxt = ', '.join('%s=%%r' % name for name in field_names)
template = '''class %(typename)s(tuple):
@ -41,7 +43,10 @@ def NamedTuple(typename, s, verbose=False):
return tuple.__new__(cls, (%(argtxt)s))
def __repr__(self):
return '%(typename)s(%(reprtxt)s)' %% self
def __replace__(self, field, value):
def __asdict__(self, dict=dict, zip=zip):
'Return a new dict mapping field names to their values'
return dict(zip(%(field_names)r, self))
def __replace__(self, field, value, dict=dict, zip=zip):
'Return a new %(typename)s object replacing one field with a new value'
return %(typename)s(**dict(zip(%(field_names)r, self) + [(field, value)])) \n''' % locals()
for i, name in enumerate(field_names):

2
Lib/test/test_collections.py
View File

@ -13,6 +13,7 @@ class TestNamedTuple(unittest.TestCase):
self.assertEqual(Point.__getitem__, tuple.__getitem__)
self.assertRaises(ValueError, NamedTuple, 'abc%', 'def ghi')
self.assertRaises(ValueError, NamedTuple, 'abc', 'def g%hi')
self.assertRaises(ValueError, NamedTuple, 'abc', '__def__ ghi')
NamedTuple('Point0', 'x1 y2') # Verify that numbers are allowed in names
def test_instance(self):
@ -32,6 +33,7 @@ class TestNamedTuple(unittest.TestCase):
self.assert_('__weakref__' not in dir(p))
self.assertEqual(p.__fields__, ('x', 'y')) # test __fields__ attribute
self.assertEqual(p.__replace__('x', 1), (1, 22)) # test __replace__ method
self.assertEqual(p.__asdict__(), dict(x=11, y=22)) # test __dict__ method
# verify that field string can have commas
Point = NamedTuple('Point', 'x, y')

90
Lib/test/test_deque.py
View File

@ -47,6 +47,44 @@ class TestBasic(unittest.TestCase):
self.assertEqual(right, range(150, 400))
self.assertEqual(list(d), range(50, 150))
def test_maxlen(self):
self.assertRaises(ValueError, deque, 'abc', -2)
d = deque(range(10), maxlen=3)
self.assertEqual(repr(d), 'deque([7, 8, 9], maxlen=3)')
self.assertEqual(list(d), range(7, 10))
self.assertEqual(d, deque(range(10), 3))
d.append(10)
self.assertEqual(list(d), range(8, 11))
d.appendleft(7)
self.assertEqual(list(d), range(7, 10))
d.extend([10, 11])
self.assertEqual(list(d), range(9, 12))
d.extendleft([8, 7])
self.assertEqual(list(d), range(7, 10))
d = deque(xrange(200), maxlen=10)
d.append(d)
try:
fo = open(test_support.TESTFN, "wb")
print >> fo, d,
fo.close()
fo = open(test_support.TESTFN, "rb")
self.assertEqual(fo.read(), repr(d))
finally:
fo.close()
os.remove(test_support.TESTFN)
d = deque(range(10), maxlen=-1)
self.assertEqual(repr(d), 'deque([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])')
try:
fo = open(test_support.TESTFN, "wb")
print >> fo, d,
fo.close()
fo = open(test_support.TESTFN, "rb")
self.assertEqual(fo.read(), repr(d))
finally:
fo.close()
os.remove(test_support.TESTFN)
def test_comparisons(self):
d = deque('xabc'); d.popleft()
for e in [d, deque('abc'), deque('ab'), deque(), list(d)]:
@ -254,7 +292,7 @@ class TestBasic(unittest.TestCase):
os.remove(test_support.TESTFN)
def test_init(self):
self.assertRaises(TypeError, deque, 'abc', 2);
self.assertRaises(TypeError, deque, 'abc', 2, 3);
self.assertRaises(TypeError, deque, 1);
def test_hash(self):
@ -339,13 +377,13 @@ class TestBasic(unittest.TestCase):
self.assertNotEqual(id(d), id(e))
self.assertEqual(list(d), list(e))
def test_pickle_recursive(self):
d = deque('abc')
d.append(d)
for i in (0, 1, 2):
e = pickle.loads(pickle.dumps(d, i))
self.assertNotEqual(id(d), id(e))
self.assertEqual(id(e), id(e[-1]))
## def test_pickle_recursive(self):
## d = deque('abc')
## d.append(d)
## for i in (0, 1, 2):
## e = pickle.loads(pickle.dumps(d, i))
## self.assertNotEqual(id(d), id(e))
## self.assertEqual(id(e), id(e[-1]))
def test_deepcopy(self):
mut = [10]
@ -451,24 +489,24 @@ class TestSubclass(unittest.TestCase):
self.assertEqual(type(d), type(e))
self.assertEqual(list(d), list(e))
def test_pickle(self):
d = Deque('abc')
d.append(d)
e = pickle.loads(pickle.dumps(d))
self.assertNotEqual(id(d), id(e))
self.assertEqual(type(d), type(e))
dd = d.pop()
ee = e.pop()
self.assertEqual(id(e), id(ee))
self.assertEqual(d, e)
d.x = d
e = pickle.loads(pickle.dumps(d))
self.assertEqual(id(e), id(e.x))
d = DequeWithBadIter('abc')
self.assertRaises(TypeError, pickle.dumps, d)
## def test_pickle(self):
## d = Deque('abc')
## d.append(d)
##
## e = pickle.loads(pickle.dumps(d))
## self.assertNotEqual(id(d), id(e))
## self.assertEqual(type(d), type(e))
## dd = d.pop()
## ee = e.pop()
## self.assertEqual(id(e), id(ee))
## self.assertEqual(d, e)
##
## d.x = d
## e = pickle.loads(pickle.dumps(d))
## self.assertEqual(id(e), id(e.x))
##
## d = DequeWithBadIter('abc')
## self.assertRaises(TypeError, pickle.dumps, d)
def test_weakref(self):
d = deque('gallahad')

2
Misc/NEWS
View File

@ -270,6 +270,8 @@ Core and builtins
Library
-------
- collections.deque() now supports a "maxlen" argument.
- itertools.count() is no longer bounded to LONG_MAX. Formerly, it raised
an OverflowError. Now, automatically shifts from ints to longs.

186
Modules/_collectionsmodule.c
View File

@ -83,10 +83,27 @@ typedef struct {
int leftindex; /* in range(BLOCKLEN) */
int rightindex; /* in range(BLOCKLEN) */
int len;
int maxlen;
long state; /* incremented whenever the indices move */
PyObject *weakreflist; /* List of weak references */
} dequeobject;
/* The deque's size limit is d.maxlen. The limit can be zero or positive.
* If there is no limit, then d.maxlen == -1.
*
* After an item is added to a deque, we check to see if the size has grown past
* the limit. If it has, we get the size back down to the limit by popping an
* item off of the opposite end. The methods that can trigger this are append(),
* appendleft(), extend(), and extendleft().
*/
#define TRIM(d, popfunction) \
if (d->maxlen != -1 && d->len > d->maxlen) { \
PyObject *rv = popfunction(d, NULL); \
assert(rv != NULL && d->len <= d->maxlen); \
Py_DECREF(rv); \
}
static PyTypeObject deque_type;
static PyObject *
@ -95,9 +112,6 @@ deque_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
dequeobject *deque;
block *b;
if (type == &deque_type && !_PyArg_NoKeywords("deque()", kwds))
return NULL;
/* create dequeobject structure */
deque = (dequeobject *)type->tp_alloc(type, 0);
if (deque == NULL)
@ -117,54 +131,11 @@ deque_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
deque->len = 0;
deque->state = 0;
deque->weakreflist = NULL;
deque->maxlen = -1;
return (PyObject *)deque;
}
static PyObject *
deque_append(dequeobject *deque, PyObject *item)
{
deque->state++;
if (deque->rightindex == BLOCKLEN-1) {
block *b = newblock(deque->rightblock, NULL, deque->len);
if (b == NULL)
return NULL;
assert(deque->rightblock->rightlink == NULL);
deque->rightblock->rightlink = b;
deque->rightblock = b;
deque->rightindex = -1;
}
Py_INCREF(item);
deque->len++;
deque->rightindex++;
deque->rightblock->data[deque->rightindex] = item;
Py_RETURN_NONE;
}
PyDoc_STRVAR(append_doc, "Add an element to the right side of the deque.");
static PyObject *
deque_appendleft(dequeobject *deque, PyObject *item)
{
deque->state++;
if (deque->leftindex == 0) {
block *b = newblock(NULL, deque->leftblock, deque->len);
if (b == NULL)
return NULL;
assert(deque->leftblock->leftlink == NULL);
deque->leftblock->leftlink = b;
deque->leftblock = b;
deque->leftindex = BLOCKLEN;
}
Py_INCREF(item);
deque->len++;
deque->leftindex--;
deque->leftblock->data[deque->leftindex] = item;
Py_RETURN_NONE;
}
PyDoc_STRVAR(appendleft_doc, "Add an element to the left side of the deque.");
static PyObject *
deque_pop(dequeobject *deque, PyObject *unused)
{
@ -239,6 +210,52 @@ deque_popleft(dequeobject *deque, PyObject *unused)
PyDoc_STRVAR(popleft_doc, "Remove and return the leftmost element.");
static PyObject *
deque_append(dequeobject *deque, PyObject *item)
{
deque->state++;
if (deque->rightindex == BLOCKLEN-1) {
block *b = newblock(deque->rightblock, NULL, deque->len);
if (b == NULL)
return NULL;
assert(deque->rightblock->rightlink == NULL);
deque->rightblock->rightlink = b;
deque->rightblock = b;
deque->rightindex = -1;
}
Py_INCREF(item);
deque->len++;
deque->rightindex++;
deque->rightblock->data[deque->rightindex] = item;
TRIM(deque, deque_popleft);
Py_RETURN_NONE;
}
PyDoc_STRVAR(append_doc, "Add an element to the right side of the deque.");
static PyObject *
deque_appendleft(dequeobject *deque, PyObject *item)
{
deque->state++;
if (deque->leftindex == 0) {
block *b = newblock(NULL, deque->leftblock, deque->len);
if (b == NULL)
return NULL;
assert(deque->leftblock->leftlink == NULL);
deque->leftblock->leftlink = b;
deque->leftblock = b;
deque->leftindex = BLOCKLEN;
}
Py_INCREF(item);
deque->len++;
deque->leftindex--;
deque->leftblock->data[deque->leftindex] = item;
TRIM(deque, deque_pop);
Py_RETURN_NONE;
}
PyDoc_STRVAR(appendleft_doc, "Add an element to the left side of the deque.");
static PyObject *
deque_extend(dequeobject *deque, PyObject *iterable)
{
@ -266,6 +283,7 @@ deque_extend(dequeobject *deque, PyObject *iterable)
deque->len++;
deque->rightindex++;
deque->rightblock->data[deque->rightindex] = item;
TRIM(deque, deque_popleft);
}
Py_DECREF(it);
if (PyErr_Occurred())
@ -303,6 +321,7 @@ deque_extendleft(dequeobject *deque, PyObject *iterable)
deque->len++;
deque->leftindex--;
deque->leftblock->data[deque->leftindex] = item;
TRIM(deque, deque_pop);
}
Py_DECREF(it);
if (PyErr_Occurred())
@ -579,8 +598,8 @@ deque_nohash(PyObject *self)
static PyObject *
deque_copy(PyObject *deque)
{
return PyObject_CallFunctionObjArgs((PyObject *)(Py_Type(deque)),
deque, NULL);
return PyObject_CallFunction((PyObject *)(Py_Type(deque)), "Oi",
deque, ((dequeobject *)deque)->maxlen, NULL);
}
PyDoc_STRVAR(copy_doc, "Return a shallow copy of a deque.");
@ -588,21 +607,22 @@ PyDoc_STRVAR(copy_doc, "Return a shallow copy of a deque.");
static PyObject *
deque_reduce(dequeobject *deque)
{
PyObject *dict, *result, *it;
PyObject *dict, *result, *aslist;
dict = PyObject_GetAttrString((PyObject *)deque, "__dict__");
if (dict == NULL) {
if (dict == NULL)
PyErr_Clear();
dict = Py_None;
Py_INCREF(dict);
}
it = PyObject_GetIter((PyObject *)deque);
if (it == NULL) {
aslist = PySequence_List((PyObject *)deque);
if (aslist == NULL) {
Py_DECREF(dict);
return NULL;
}
result = Py_BuildValue("O()ON", Py_Type(deque), dict, it);
Py_DECREF(dict);
if (dict == NULL)
result = Py_BuildValue("O(Oi)", Py_Type(deque), aslist, deque->maxlen);
else
result = Py_BuildValue("O(Oi)O", Py_Type(deque), aslist, deque->maxlen, dict);
Py_XDECREF(dict);
Py_DECREF(aslist);
return result;
}
@ -611,7 +631,7 @@ PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
static PyObject *
deque_repr(PyObject *deque)
{
PyObject *aslist, *result, *fmt;
PyObject *aslist, *result, *fmt; /*, *limit; */
int i;
i = Py_ReprEnter(deque);
@ -626,14 +646,17 @@ deque_repr(PyObject *deque)
Py_ReprLeave(deque);
return NULL;
}
fmt = PyString_FromString("deque(%r)");
if (((dequeobject *)deque)->maxlen != -1)
fmt = PyString_FromFormat("deque(%%r, maxlen=%i)",
((dequeobject *)deque)->maxlen);
else
fmt = PyString_FromString("deque(%r)");
if (fmt == NULL) {
Py_DECREF(aslist);
Py_ReprLeave(deque);
return NULL;
}
result = PyString_Format(fmt, aslist);
result = PyString_Format(fmt, aslist);
Py_DECREF(fmt);
Py_DECREF(aslist);
Py_ReprLeave(deque);
@ -652,9 +675,7 @@ deque_tp_print(PyObject *deque, FILE *fp, int flags)
if (i != 0) {
if (i < 0)
return i;
Py_BEGIN_ALLOW_THREADS
fputs("[...]", fp);
Py_END_ALLOW_THREADS
return 0;
}
@ -662,13 +683,9 @@ deque_tp_print(PyObject *deque, FILE *fp, int flags)
if (it == NULL)
return -1;
Py_BEGIN_ALLOW_THREADS
fputs("deque([", fp);
Py_END_ALLOW_THREADS
while ((item = PyIter_Next(it)) != NULL) {
Py_BEGIN_ALLOW_THREADS
fputs(emit, fp);
Py_END_ALLOW_THREADS
emit = separator;
if (PyObject_Print(item, fp, 0) != 0) {
Py_DECREF(item);
@ -682,9 +699,11 @@ deque_tp_print(PyObject *deque, FILE *fp, int flags)
Py_DECREF(it);
if (PyErr_Occurred())
return -1;
Py_BEGIN_ALLOW_THREADS
fputs("])", fp);
Py_END_ALLOW_THREADS
if (((dequeobject *)deque)->maxlen == -1)
fputs("])", fp);
else
fprintf(fp, "], maxlen=%d)", ((dequeobject *)deque)->maxlen);
return 0;
}
@ -767,13 +786,19 @@ done:
}
static int
deque_init(dequeobject *deque, PyObject *args, PyObject *kwds)
deque_init(dequeobject *deque, PyObject *args, PyObject *kwdargs)
{
PyObject *iterable = NULL;
int maxlen = -1;
char *kwlist[] = {"iterable", "maxlen", 0};
if (!PyArg_UnpackTuple(args, "deque", 0, 1, &iterable))
if (!PyArg_ParseTupleAndKeywords(args, kwdargs, "|Oi:deque", kwlist, &iterable, &maxlen))
return -1;
if (maxlen < -1) {
PyErr_SetString(PyExc_ValueError, "maxlen must be -1 or greater");
return -1;
}
deque->maxlen = maxlen;
if (iterable != NULL) {
PyObject *rv = deque_extend(deque, iterable);
if (rv == NULL)
@ -828,7 +853,7 @@ static PyMethodDef deque_methods[] = {
};
PyDoc_STRVAR(deque_doc,
"deque(iterable) --> deque object\n\
"deque(iterable[, maxlen]) --> deque object\n\
\n\
Build an ordered collection accessible from endpoints only.");
@ -1198,24 +1223,15 @@ static int
defdict_print(defdictobject *dd, FILE *fp, int flags)
{
int sts;
Py_BEGIN_ALLOW_THREADS
fprintf(fp, "defaultdict(");
Py_END_ALLOW_THREADS
if (dd->default_factory == NULL) {
Py_BEGIN_ALLOW_THREADS
if (dd->default_factory == NULL)
fprintf(fp, "None");
Py_END_ALLOW_THREADS
}
else {
PyObject_Print(dd->default_factory, fp, 0);
}
Py_BEGIN_ALLOW_THREADS
fprintf(fp, ", ");
Py_END_ALLOW_THREADS
sts = PyDict_Type.tp_print((PyObject *)dd, fp, 0);
Py_BEGIN_ALLOW_THREADS
fprintf(fp, ")");
Py_END_ALLOW_THREADS
return sts;
}