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Jython is an implementation of the high-level, dynamic, object-oriented
language Python written in 100% Pure Java, and seamlessly integrated with
the Java platform. It thus allows you to run Python on any Java platform.
/* Copyright (c) Jython Developers */
package org.python.modules;
import java.util.ArrayList;
import java.util.List;
import org.python.core.ArgParser;
import org.python.core.ClassDictInit;
import org.python.core.Py;
import org.python.core.PyException;
import org.python.core.PyInteger;
import org.python.core.PyIterator;
import org.python.core.PyNone;
import org.python.core.PyObject;
import org.python.core.PyString;
import org.python.core.PyTuple;
import org.python.core.PyXRange;
/**
* Functional tools for creating and using iterators. Java implementation of the CPython module
* itertools.
*
* @since 2.5
*/
public class itertools implements ClassDictInit {
public static PyString __doc__ = new PyString(
"Functional tools for creating and using iterators.\n\nInfinite iterators:\n"
+ "count([n]) --> n, n+1, n+2, ...\ncycle(p) --> p0, p1, ... plast, p0, p1, ...\n"
+ "repeat(elem [,n]) --> elem, elem, elem, ... endlessly or up to n times\n\n"
+ "Iterators terminating on the shortest input sequence:"
+ "\nizip(p, q, ...) --> (p[0], q[0]), (p[1], q[1]), ... \n"
+ "ifilter(pred, seq) --> elements of seq where pred(elem) is True\n"
+ "ifilterfalse(pred, seq) --> elements of seq where pred(elem) is False\n"
+ "islice(seq, [start,] stop [, step]) --> elements from\n seq[start:stop:step]\n"
+ "imap(fun, p, q, ...) --> fun(p0, q0), fun(p1, q1), ...\n"
+ "starmap(fun, seq) --> fun(*seq[0]), fun(*seq[1]), ...\n"
+ "chain(p, q, ...) --> p0, p1, ... plast, q0, q1, ... \n"
+ "takewhile(pred, seq) --> seq[0], seq[1], until pred fails\n"
+ "dropwhile(pred, seq) --> seq[n],seq[n+1], starting when pred fails\n"
+ "groupby(iterable[, keyfunc]) -> create an iterator which returns\n"
+ "(key, sub-iterator) grouped by each value of key(value)."
+ "tee(iterable, n=2) --> tuple of n independent iterators.");
/**
* Iterator base class used by most methods.
*/
static abstract class ItertoolsIterator extends PyIterator {
/**
* Returns the next element from an iterator. If it raises/throws StopIteration just store
* the Exception and return null according to PyIterator practice.
*/
protected PyObject nextElement(PyObject pyIter) {
PyObject element = null;
try {
element = pyIter.__iternext__();//next();
} catch (PyException pyEx) {
if (pyEx.match(Py.StopIteration)) {
// store exception - will be used by PyIterator.next()
stopException = pyEx;
} else {
throw pyEx;
}
}
return element;
}
}
public static void classDictInit(PyObject dict) {
}
public static PyString __doc__count = new PyString(
"count([firstval]) --> count object\n\nReturn a count object whose .next() "
+ "method returns consecutive\nintegers starting from zero or, if specified, from firstval.");
/**
* Creates an iterator that returns consecutive integers starting at init.
*/
public static PyIterator count(final int init) {
return new PyIterator() {
int counter = init;
public PyObject __iternext__() {
return new PyInteger(counter++);
}
public PyString __repr__() {
return (PyString)(Py.newString("count(%d)").__mod__(Py.newInteger(counter)));
}
};
}
/**
* Creates an iterator that returns consecutive integers starting at 0.
*/
public static PyIterator count() {
return itertools.count(0);
}
public static PyString __doc__cycle = new PyString(
"cycle(iterable) --> cycle object\n\nReturn elements from the iterable "
+ "until itis exhausted.\nThen repeat the sequence indefinitely.");
/**
* Returns an iterator that iterates over an iterable, saving the values for each iteration.
* When the iterable is exhausted continues to iterate over the saved values indefinitely.
*/
public static PyIterator cycle(final PyObject sequence) {
return new ItertoolsIterator() {
List saved = new ArrayList();
int counter = 0;
PyObject iter = sequence.__iter__();
boolean save = true;
public PyObject __iternext__() {
if (save) {
PyObject obj = nextElement(iter);
if (obj != null) {
saved.add(obj);
return obj;
} else {
save = false;
}
}
if (saved.size() == 0) {
return null;
}
// pick element from saved List
if (counter >= saved.size()) {
// start over again
counter = 0;
}
return saved.get(counter++);
}
};
}
public static PyString __doc__chain = new PyString(
"chain(*iterables) --> chain object\n\nReturn a chain object "
+ "whose .next() method returns elements from the\nfirst iterable until it is exhausted, then elements"
+ " from the next\niterable, until all of the iterables are exhausted.");
/**
* Creates an iterator that iterates over a chain of iterables.
*/
public static PyIterator chain(final PyObject[] iterables) {
final PyObject[] iterators = new PyObject[iterables.length];
for (int i = 0; i < iterables.length; i++) {
iterators[i] = iterables[i].__iter__();
}
return new ItertoolsIterator() {
int iteratorIndex = 0;
public PyObject __iternext__() {
PyObject next = null;
for (; iteratorIndex < iterators.length; iteratorIndex++) {
next = nextElement(iterators[iteratorIndex]);
if (next != null) {
break;
}
}
return next;
}
};
}
public static PyString __doc__repeat = new PyString(
"'repeat(element [,times]) -> create an iterator which returns the element\n"
+ "for the specified number of times. If not specified, returns the element\nendlessly.");
/**
* Creates an iterator that returns the same object the number of times given by
* times.
*/
public static PyIterator repeat(final PyObject object, final int times) {
return new PyIterator() {
int counter = times;
public PyObject __iternext__() {
if (counter > 0) {
counter--;
return object;
}
return null;
}
public int __len__() {
return times;
}
public PyString __repr__() {
return (PyString)(Py.newString("repeat(%r, %d)").
__mod__(new PyTuple(object, Py.newInteger(counter))));
}
};
}
/**
* Creates an iterator that returns the same object over and over again.
*/
public static PyIterator repeat(final PyObject object) {
return new PyIterator() {
public PyObject __iternext__() {
return object;
}
public PyString __repr__() {
return (PyString)(Py.newString("repeat(%r)").
__mod__(new PyTuple(object)));
}
};
}
public static PyString __doc__imap = new PyString(
"'map(func, *iterables) --> imap object\n\nMake an iterator that computes the "
+ "function using arguments from\neach of the iterables.\tLike map() except that it returns\n"
+ "an iterator instead of a list and that it stops when the shortest\niterable is exhausted "
+ "instead of filling in None for shorter\niterables.");
/**
* Works as __builtin__.map() but returns an iterator instead of a list. (Code in
* this method is based on __builtin__.map()).
*/
public static PyIterator imap(PyObject[] argstar) {
final int n = argstar.length - 1;
if (n < 1) {
throw Py.TypeError("imap requires at least two arguments");
}
final PyObject callable = argstar[0];
final PyObject[] iters = new PyObject[n];
for (int j = 0; j < n; j++) {
iters[j] = Py.iter(argstar[j + 1], "argument " + (j + 1)
+ " to imap() must support iteration");
}
return new PyIterator() {
PyObject[] args = new PyObject[n];
PyObject element = null;
public PyObject __iternext__() {
for (int i = 0; i < n; i++) {
if ((element = iters[i].__iternext__()) != null) {
// collect the arguments for the callable
args[i] = element;
} else {
// break iteration
return null;
}
}
if (callable == Py.None) {
// if None is supplied as callable we just return what's in
// the iterable(s)
if (n == 1) {
return args[0];
} else {
return new PyTuple(args.clone());
}
} else {
return callable.__call__(args);
}
}
};
}
public static PyString __doc__islice = new PyString(
"islice(iterable, [start,] stop [, step]) --> islice object\n"
+ "\nReturn an iterator whose next() method returns selected values from an\n"
+ "iterable. If start is specified, will skip all preceding elements;\notherwise, start defaults to zero."
+ "Step defaults to one. If\nspecified as another value, step determines how manyvalues are \n"
+ "skipped between successive calls. Works like a slice() on a list\nbut returns an iterator.");
private static int py2int(PyObject obj, int defaultValue, String msg) {
if (obj instanceof PyNone) {
return defaultValue;
} else {
int value = defaultValue;
try {
value = Py.py2int(obj);
}
catch (PyException pyEx) {
if (pyEx.match(Py.TypeError)) {
throw Py.ValueError(msg);
} else {
throw pyEx;
}
}
return value;
}
}
/**
* Creates an iterator that returns selected values from an iterable.
*
* @param startObj
* the index of where in the iterable to start returning values
* @param stopObj
* the index of where in the iterable to stop returning values
* @param stepObj
* the number of steps to take beween each call to next()
*/
public static PyIterator islice(final PyObject iterable, PyObject startObj,
PyObject stopObj, PyObject stepObj) {
final int stop = py2int(stopObj, 0, "Stop argument must be a non-negative integer or None");
final int start = py2int(startObj, 0, "Start argument must be a non-negative integer or None");
final int step = py2int(stepObj, 1, "Step argument must be a non-negative integer or None");
final boolean stopNone = stopObj instanceof PyNone;
if (start < 0 || step < 0 || stop < 0) {
throw Py.ValueError("Indices for islice() must be non-negative integers");
}
if (step == 0) {
throw Py.ValueError("Step must be one or larger for islice()");
}
return new ItertoolsIterator() {
int counter = start;
int lastCount = 0;
PyObject iter = iterable.__iter__();
public PyObject __iternext__() {
PyObject result = null;
if (counter >= stop && !stopNone) {
return null;
}
while (lastCount <= counter) {
result = nextElement(iter);
lastCount++;
}
counter += step;
return result;
}
};
}
/**
* @see #islice(PyObject, PyObject, PyObject, PyObject) startObj defaults to 0 and stepObj to 1
*/
public static PyIterator islice(PyObject iterable, PyObject stopObj) {
return islice(iterable, new PyInteger(0), stopObj, new PyInteger(1));
}
/**
* @see #islice(PyObject, PyObject, PyObject, PyObject) stepObj defaults to 1
*/
public static PyIterator islice(PyObject iterable, PyObject start,
PyObject stopObj) {
return islice(iterable, start, stopObj, new PyInteger(1));
}
/**
* Iterator base class for iterators returned by ifilter and
* ifilterfalse.
*/
static class FilterIterator extends ItertoolsIterator {
private PyObject predicate;
private PyObject iterator;
private boolean filterTrue;
FilterIterator(PyObject predicate, PyObject iterable, boolean filterTrue) {
if (predicate instanceof PyNone) {
this.predicate = null;
} else {
this.predicate = predicate;
}
this.iterator = iterable.__iter__();
this.filterTrue = filterTrue;
}
public PyObject __iternext__() {
while (true) {
PyObject element = nextElement(iterator);
if (element != null) {
// the boolean value of calling predicate with the element
// or if predicate is null/None of the element itself
boolean booleanValue = predicate != null ? predicate
.__call__(element).__nonzero__() : element
.__nonzero__();
if (booleanValue == filterTrue) {
// if the boolean value is the same as filterTrue return
// the element
// for ifilter filterTrue is always true, for
// ifilterfalse always false
return element;
}
} else {
return null;
}
}
}
}
public static PyString __doc__ifilter = new PyString(
"ifilter(function or None, sequence) --> ifilter object\n\n"
+ "Return those items of sequence for which function(item) is true.\nIf function is None, "
+ "return the items that are true.");
/**
* Creates an iterator that returns the items of the iterable for which
* predicate(item) is true. If predicate is null
* (None) return the items that are true.
*/
public static PyIterator ifilter(PyObject predicate, PyObject iterable) {
return new FilterIterator(predicate, iterable, true);
}
public static PyString __doc__ifilterfalse = new PyString(
"'ifilterfalse(function or None, sequence) --> ifilterfalse object\n\n"
+ "Return those items of sequence for which function(item) is false.\nIf function is None, "
+ "return the items that are false.'");
/**
* Creates an iterator that returns the items of the iterable for which
* predicate(item) is false. If predicate is null
* (None) return the items that are false.
*/
public static PyIterator ifilterfalse(PyObject predicate, PyObject iterable) {
return new FilterIterator(predicate, iterable, false);
}
public static PyString __doc__izip = new PyString(
"izip(iter1 [,iter2 [...]]) --> izip object\n\nReturn an izip object "
+ "whose .next() method returns a tuple where\nthe i-th element comes from the i-th iterable argument. "
+ "The .next()\nmethod continues until the shortest iterable in the argument sequence\nis exhausted and then it "
+ "raises StopIteration. Works like the zip()\nfunction but consumes less memory by returning an iterator "
+ "instead of\na list.");
/**
* Create an iterator whose next() method returns a tuple where the i-th element
* comes from the i-th iterable argument. Continues until the shortest iterable is exhausted.
* (Code in this method is based on __builtin__.zip()).
*
*/
public static PyIterator izip(PyObject[] argstar) {
final int itemsize = argstar.length;
if (itemsize == 0) {
return (PyIterator)(new PyXRange(0).__iter__());
}
// Type check the arguments; they must be sequences.
final PyObject[] iters = new PyObject[itemsize];
for (int i = 0; i < itemsize; i++) {
PyObject iter = argstar[i].__iter__();
if (iter == null) {
throw Py.TypeError("izip argument #" + (i + 1)
+ " must support iteration");
}
iters[i] = iter;
}
return new ItertoolsIterator() {
public PyObject __iternext__() {
if (itemsize == 0)
return null;
PyObject[] next = new PyObject[itemsize];
PyObject item;
for (int i = 0; i < itemsize; i++) {
item = nextElement(iters[i]);
if (item == null) {
return null;
}
next[i] = item;
}
return new PyTuple(next);
}
};
}
public static PyString __doc__starmap = new PyString(
"starmap(function, sequence) --> starmap object\n\nReturn an "
+ "iterator whose values are returned from the function evaluated\nwith an argument tuple taken from the "
+ "given sequence.");
/**
* Create an iterator whose next() method returns the result
* of calling the function (first argument) with a tuple of arguments
* returned from the iterable (second argument).
*
* @param starargs
* [0] = callable function, [1] = iterable with argument tuples
*/
public static PyIterator starmap(PyObject[] starargs) {
if (starargs.length != 2) {
throw Py.TypeError("starmap requires 2 arguments, got "
+ starargs.length);
}
final PyObject callable = starargs[0];
final PyObject iterator = starargs[1].__iter__();
return new ItertoolsIterator() {
public PyObject __iternext__() {
PyObject args = nextElement(iterator);
PyObject result = null;
if (args != null) {
if (!args.getClass().isAssignableFrom(PyTuple.class)) {
throw Py.TypeError("iterator must return a tuple");
}
PyTuple argTuple = (PyTuple) args;
// convert to array of PyObjects in call to function
result = callable.__call__(argTuple.getArray());
}
return result;
}
};
}
/**
* Iterator base class used by dropwhile() and takewhile.
*/
static class WhileIterator extends ItertoolsIterator {
private PyObject iterator;
private PyObject predicate;
// flag that indicates if the iterator shoul drop or return arguments "while" the predicate is true
private boolean drop;
// flag that is set once the predicate is satisfied
private boolean predicateSatisfied;
WhileIterator(PyObject predicate, PyObject iterable, boolean drop) {
this.predicate = predicate;
iterator = iterable.__iter__();
this.drop = drop;
}
public PyObject __iternext__() {
while (true) {
PyObject element = nextElement(iterator);
if (element != null) {
if (!predicateSatisfied) {
// the predicate is not satisfied yet (or still satisfied in the case of drop beeing
// false), so we need to check it
if (predicate.__call__(element).__nonzero__() != drop) {
predicateSatisfied = drop;
return element;
}
predicateSatisfied = !drop;
} else {
if (drop) {
return element;
} else {
// end iteration if predicate is false and drop is false
return null;
}
}
} else {
// end iteration
return null;
}
}
}
}
public static PyString __doc__dropwhile = new PyString(
"dropwhile(predicate, iterable) --> dropwhile object\n\nDrop items "
+ "from the iterable while predicate(item) is true.\nAfterwards, return every element until theiterable is exhausted.");
/**
* Create an iterator that drops items from the iterable while prdicate(item)
* equals true. After which every remaining item of the iterable is returned.
*/
public static PyIterator dropwhile(PyObject predicate, PyObject iterable) {
return new WhileIterator(predicate, iterable, true);
}
public static PyString __doc__takewhile = new PyString(
"takewhile(predicate, iterable) --> takewhile object\n\nReturn "
+ "successive entries from an iterable as long as the \npredicate evaluates to true for each entry.");
/**
* Create an iterator that returns items from the iterable while predicate(item)
* is true. After which iteration is stopped.
*/
public static PyIterator takewhile(PyObject predicate, PyObject iterable) {
return new WhileIterator(predicate, iterable, false);
}
private final static class GroupBy extends ItertoolsIterator {
private final PyObject iterator;
private final PyObject keyFunc;
private PyObject currentKey;
private PyObject currentValue;
private PyObject targetKey;
private GroupBy(PyObject iterable, PyObject key) {
iterator = iterable.__iter__();
keyFunc = key;
targetKey = currentKey = currentValue = new PyXRange(0);
}
public PyObject __iternext__() {
while (currentKey.equals(targetKey)) {
currentValue = nextElement(iterator);
if (currentValue == null) {
return null;
}
if (keyFunc == null) {
currentKey = currentValue;
} else {
currentKey = keyFunc.__call__(currentValue);
}
}
targetKey = currentKey;
return new PyTuple(currentKey, new GroupByIterator());
}
private class GroupByIterator extends ItertoolsIterator {
private boolean completed = false;
public PyObject __iternext__() {
final PyObject item = currentValue;
if (completed) {
return null;
}
currentValue = nextElement(iterator);
if (currentValue == null) {
completed = true;
} else {
if (keyFunc == null) {
currentKey = currentValue;
} else {
currentKey = keyFunc.__call__(currentValue);
}
}
if (!currentKey.equals(targetKey)) {
completed = true;
}
return item;
}
}
}
public static PyString __doc__groupby = new PyString(
"groupby(iterable[, keyfunc]) -> create an iterator which returns\n" +
"(key, sub-iterator) grouped by each value of key(value).");
/**
* Create an iterator which returns the pair (key, sub-iterator) grouped by key(value).
*/
public static PyIterator groupby(PyObject [] args, String [] kws) {
ArgParser ap = new ArgParser("groupby", args, kws, "iterable", "key");
if(args.length > 2){
throw Py.TypeError("groupby takes two arguments, iterable and key");
}
PyObject iterable = ap.getPyObject(0);
PyObject key = ap.getPyObject(1, null);
return new GroupBy(iterable, key);
}
public static PyString __doc__tee = new PyString(
"tee(iterable, n=2) --> tuple of n independent iterators.");
/**
* Create a tuple of iterators, each of which is effectively a copy of iterable.
*/
public static PyTuple tee(PyObject iterable, final int n) {
return new PyTuple(PyTeeIterator.makeTees(iterable, n));
}
/**
* Create a pair of iterators, each of which is effectively a copy of iterable.
*/
public static PyTuple tee(PyObject iterable) {
return tee(iterable, 2);
}
}