Merge branch 'dwcoder-fix-iss19'

diceware/random_sources.py

@@ -131,9 +131,8 @@ class RealDiceRandomSource(object):
         We make sure that `num_rolls`, the number of rolls, is in an
         acceptable range and issue an hint about the procedure.
         """
-        if num_rolls < 1:
-            raise ValueError(
-                "Must provide at least %s items" % self.dice_sides)
+        if num_rolls == 0:
+            raise(ValueError)
         if (self.dice_sides ** num_rolls) < len(sequence):
             print(
                 "Warning: entropy is reduced! Using only first %s of %s "
@@ -150,6 +149,22 @@ class RealDiceRandomSource(object):
         """Pick one item out of `sequence`.
         """
         num_rolls = int(math.log(len(sequence), self.dice_sides))
+        use_modulo = False
+        if num_rolls < 1:
+            # If this happens, there are less values in the sequence to
+            # choose from than there are dice sides.
+            # First check whehter the length is 1. Then we don't have
+            # to do anything else
+            if len(sequence) == 1:
+                # Check whether len(sequence) is a factor of dice.sides
+                return sequence[0]
+            if self.dice_sides % len(sequence) == 0:
+                use_modulo = True
+                num_rolls = 1
+            else:
+                # otherwise We will perform one extra roll and apply modulo
+                use_modulo = True
+                num_rolls = 2
         self.pre_check(num_rolls, sequence)
         result = 0
         for i in range(num_rolls, 0, -1):
@@ -159,4 +174,6 @@ class RealDiceRandomSource(object):
                 rolled = input_func(
                     "What number shows dice number %s? " % (num_rolls - i + 1))
             result += ((self.dice_sides ** (i - 1)) * (int(rolled) - 1))
+            if use_modulo:
+                result = result % len(sequence)
         return sequence[result]

tests/test_random_sources.py

@@ -219,13 +219,6 @@ class TestRealDiceRandomSource(object):
         src = RealDiceRandomSource(None)
         assert src.choice([1, 2, 3, 4, 5, 6]) == 1
 
-    def test_choice_len_too_short(self, monkeypatch):
-        # We raise an exception if choice gets less than 6 elements.
-        self.fake_input_values(["1"], monkeypatch)
-        src = RealDiceRandomSource(None)
-        with pytest.raises(ValueError):
-            assert src.choice([1, 2, 3, 4, 5])  # list len < 6
-
     def test_choice_input_lower_value_borders(self, monkeypatch):
         # choice() does not accept "0" but it accepts "1"
         self.fake_input_values(["0", "1"], monkeypatch)
@@ -263,3 +256,29 @@ class TestRealDiceRandomSource(object):
         src.pre_check(5, ['doesntmatter'])
         out, err = capsys.readouterr()
         assert "Please roll 5 dice (or a single dice 5 times)." in out
+
+    def test_sequence_less_than_dice_sides(self, capsys, monkeypatch):
+        # Test to see whether we can use a n-sided die to choose from
+        # a sequence with less than n items
+        src = RealDiceRandomSource(None)
+        src.dice_sides = 6
+        # A length of 1 requires no rolls
+        self.fake_input_values(["1"], monkeypatch)
+        picked = src.choice([1])
+        out, err = capsys.readouterr()
+        assert "roll" not in out
+        assert picked == 1
+        # A length of 2,3 only requires 1 roll
+        for choice_length in (2, 3):
+            self.fake_input_values(["1"], monkeypatch)
+            picked = src.choice(range(1, choice_length + 1))
+            out, err = capsys.readouterr()
+            assert "roll 1 dice" in out
+            assert picked == 1
+        # A length of 4,5 requires 2 rolls
+        for choice_length in (4, 5):
+            self.fake_input_values(["1", "1"], monkeypatch)
+            picked = src.choice(range(1, choice_length + 1))
+            out, err = capsys.readouterr()
+            assert "roll 2 dice" in out
+            assert picked == 1