[Assorted-commits] SF.net SVN: assorted:[1018] python-commons/trunk/src/commons/seqs.py

[<yan...@us...>]

Revision: 1018
          http://assorted.svn.sourceforge.net/assorted/?rev=1018&view=rev
Author:   yangzhang
Date:     2008-10-14 03:35:37 +0000 (Tue, 14 Oct 2008)

Log Message:
-----------
added span, group_as_subseqs; added unittests for span, group_as_subseqs

Modified Paths:
--------------
    python-commons/trunk/src/commons/seqs.py

Modified: python-commons/trunk/src/commons/seqs.py
===================================================================
--- python-commons/trunk/src/commons/seqs.py	2008-10-14 03:34:36 UTC (rev 1017)
+++ python-commons/trunk/src/commons/seqs.py	2008-10-14 03:35:37 UTC (rev 1018)
@@ -1,6 +1,12 @@
 # -*- mode: python; tab-width: 4; indent-tabs-mode: nil; py-indent-offset: 4; -*-
 # vim:ft=python:et:sw=4:ts=4
 
+"""
+Sequences, streams, and generators.
+
+@var default_chunk_size: The default chunk size used by L{chunkify}.
+"""
+
 from __future__ import ( absolute_import, with_statement )
 
 from cStringIO import StringIO
@@ -8,15 +14,37 @@
 from struct import pack, unpack
 from contextlib import closing
 from itertools import ( chain, count, ifilterfalse, islice,
-                        izip, repeat, tee )
-from .log import warning
+                        izip, repeat, tee, takewhile )
+from commons.log import warning
 
-"""
-Sequences, streams, and generators.
+__all__ = '''
+default_chunk_size
+read_pickle
+read_pickles
+safe_pickler
+write_pickle
+streamlen
+chunkify
+total
+ClosedError
+PersistentConsumedSeq
+PersistentSeq
+pairwise
+argmax
+argmin
+all
+concat
+flatten
+grouper
+chunker
+countstep
+take
+delimit
+interleave
+group_as_subseqs
+span
+'''.split()
 
-@var default_chunk_size: The default chunk size used by L{chunkify}.
-"""
-
 default_chunk_size = 8192
 
 def read_pickle( read, init = '', length_thresh = 100000 ):
@@ -283,15 +311,6 @@
     else:
         return min((fn(e), e) for e in sequence)[1]
 
-def all(seq, pred=bool):
-    """
-    Returns C{True} if C{pred(x) is True} for every element in the
-    iterable
-    """
-    for elem in ifilterfalse(pred, seq):
-        return False
-    return True
-
 def concat(listOfLists):
     return list(chain(*listOfLists))
 
@@ -364,3 +383,53 @@
 # TODO not quite right
 def interleave(xs, ys):
     return concat(izip( xs, ys ))
+
+def span(pred, xs):
+    """
+    Returns (successes, failures), where successes is the sequence of any
+    consecutive elements at the head of L{xs} that satisfy the predicate, and
+    second is everything else.
+    """
+    xs = iter(xs)
+    first_failure = []
+    def successes():
+        for x in xs:
+            if not pred(x):
+                first_failure.append(x)
+                break
+            yield x
+    return list(successes()), chain(first_failure, xs)
+
+def group_as_subseqs(xs, key = lambda x: x):
+    """
+    Takes a sequence and breaks it up into multiple subsequences, which are
+    groups keyed on L{key}.
+    """
+    xs = iter(xs)
+    while True:
+        setfirst = False
+        for x in xs:
+            first = x
+            setfirst = True
+            break
+        if not setfirst: break # We've hit the end
+        firstkey = key(first)
+        successes, xs = span(lambda x: key(x) == firstkey, xs)
+        yield chain([first], successes)
+
+import unittest
+
+class test_seqs(unittest.TestCase):
+    def test_span(self):
+        xs,ys = span(lambda x: x < 5, range(10))
+        self.assertEqual(list(xs), range(5))
+        self.assertEqual(list(ys), range(5,10))
+    def test_group(self):
+        a,b,c,d = group_as_subseqs(range(10), lambda x: x / 3)
+        self.assertEqual(list(a), range(0,3))
+        self.assertEqual(list(b), range(3,6))
+        self.assertEqual(list(c), range(6,9))
+        self.assertEqual(list(d), range(9,10))
+
+if __name__ == '__main__':
+    unittest.main()


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