[Python-checkins] r43512 - in python/trunk: Lib/random.py Lib/test/test_random.py Misc/NEWS (original) (raw)

tim.peters python-checkins at python.org
Sat Apr 1 02:26:54 CEST 2006

• Previous message: [Python-checkins] buildbot warnings in g4 osx.4 2.4
• Next message: [Python-checkins] r43513 - in python/branches/release24-maint: Lib/random.py Lib/test/test_random.py Misc/NEWS
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

Author: tim.peters Date: Sat Apr 1 02:26:53 2006 New Revision: 43512

Modified: python/trunk/Lib/random.py python/trunk/Lib/test/test_random.py python/trunk/Misc/NEWS Log: Another crack at bug #1460340: make random.sample(dict) work, this time by ugly brute force.

Modified: python/trunk/Lib/random.py

--- python/trunk/Lib/random.py (original) +++ python/trunk/Lib/random.py Sat Apr 1 02:26:53 2006 @@ -285,6 +285,15 @@ large population: sample(xrange(10000000), 60) """

•    # XXX Although the documentation says `population` is "a sequence",

•    # XXX attempts are made to cater to any iterable with a __len__

•    # XXX method.  This has had mixed success.  Examples from both

•    # XXX sides:  sets work fine, and should become officially supported;

•    # XXX dicts are much harder, and have failed in various subtle

•    # XXX ways across attempts.  Support for mapping types should probably

•    # XXX be dropped (and users should pass mapping.keys() or .values()

•    # XXX explicitly).

•     # Sampling without replacement entails tracking either potential
      # selections (the pool) in a list or previous selections in a set.

@@ -304,7 +313,9 @@ setsize = 21 # size of a small set minus size of an empty list if k > 5: setsize += 4 ** _ceil(_log(k * 3, 4)) # table size for big sets

•    if n <= setsize:    # is an n-length list smaller than a k-length set

•    if n <= setsize or hasattr(population, "keys"):

•        # An n-length list is smaller than a k-length set, or this is a

•        # mapping type so the other algorithm wouldn't work.
         pool = list(population)
         for i in xrange(k):         # invariant:  non-selected at [0,n-i)
             j = _int(random() * (n-i))

@@ -320,10 +331,10 @@ j = _int(random() * n) selected_add(j) result[i] = population[j]

•        except (TypeError, KeyError):   # handle sets and dictionaries

•        except (TypeError, KeyError):   # handle (at least) sets
             if isinstance(population, list):
                 raise

•            return self.sample(list(population), k)

•            return self.sample(tuple(population), k)
     return result

-------------------- real-valued distributions -------------------

Modified: python/trunk/Lib/test/test_random.py

--- python/trunk/Lib/test/test_random.py (original) +++ python/trunk/Lib/test/test_random.py Sat Apr 1 02:26:53 2006 @@ -93,12 +93,28 @@ self.gen.sample(set(range(20)), 2) self.gen.sample(range(20), 2) self.gen.sample(xrange(20), 2)

•    self.gen.sample(dict.fromkeys('abcdefghijklmnopqrst'), 2)
     self.gen.sample(str('abcdefghijklmnopqrst'), 2)
     self.gen.sample(tuple('abcdefghijklmnopqrst'), 2)

• def test_sample_on_dicts(self):

•    self.gen.sample(dict.fromkeys('abcdefghijklmnopqrst'), 2)

•     # SF bug #1460340 -- random.sample can raise KeyError
      a = dict.fromkeys(range(10)+range(10,100,2)+range(100,110))

•    self.gen.sample(a,3)

•    self.gen.sample(a, 3)

•    # A followup to bug #1460340:  sampling from a dict could return

•    # a subset of its keys or of its values, depending on the size of

•    # the subset requested.

•    N = 30

•    d = dict((i, complex(i, i)) for i in xrange(N))

•    for k in xrange(N+1):

•        samp = self.gen.sample(d, k)

•        # Verify that we got ints back (keys); the values are complex.

•        for x in samp:

•            self.assert_(type(x) is int)

•    samp.sort()

•    self.assertEqual(samp, range(N))

  def test_gauss(self): # Ensure that the seed() method initializes all the hidden state. In

Modified: python/trunk/Misc/NEWS

--- python/trunk/Misc/NEWS (original) +++ python/trunk/Misc/NEWS Sat Apr 1 02:26:53 2006 @@ -489,6 +489,11 @@ Library

+- Bug #1460340: random.sample(dict) failed in various ways. Dicts + aren't officially supported here, and trying to use them will probably + raise an exception some day. But dicts have been allowed, and "mostly + worked", so support for them won't go away without warning. + - Bug #1445068: getpass.getpass() can now be given an explicit stream argument to specify where to write the prompt.

• Previous message: [Python-checkins] buildbot warnings in g4 osx.4 2.4
• Next message: [Python-checkins] r43513 - in python/branches/release24-maint: Lib/random.py Lib/test/test_random.py Misc/NEWS
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

More information about the Python-checkins mailing list