diff options
| -rw-r--r-- | Lib/random.py | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/Lib/random.py b/Lib/random.py index 6debaf3..4d29080 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -75,6 +75,7 @@ used to "move backward in time": from math import log as _log, exp as _exp, pi as _pi, e as _e from math import sqrt as _sqrt, acos as _acos, cos as _cos, sin as _sin +from math import floor as _floor __all__ = ["Random","seed","random","uniform","randint","choice", "randrange","shuffle","normalvariate","lognormvariate", @@ -299,7 +300,7 @@ class Random: """ # This code is a bit messy to make it fast for the - # common case while still doing adequate error checking + # common case while still doing adequate error checking. istart = int(start) if istart != start: raise ValueError, "non-integer arg 1 for randrange()" @@ -307,14 +308,26 @@ class Random: if istart > 0: return int(self.random() * istart) raise ValueError, "empty range for randrange()" + + # stop argument supplied. istop = int(stop) if istop != stop: raise ValueError, "non-integer stop for randrange()" + if step == 1 and istart < istop: + try: + return istart + int(self.random()*(istop - istart)) + except OverflowError: + # This can happen if istop-istart > sys.maxint + 1, and + # multiplying by random() doesn't reduce it to something + # <= sys.maxint. We know that the overall result fits + # in an int, and can still do it correctly via math.floor(). + # But that adds another function call, so for speed we + # avoided that whenever possible. + return int(istart + _floor(self.random()*(istop - istart))) if step == 1: - if istart < istop: - return istart + int(self.random() * - (istop - istart)) raise ValueError, "empty range for randrange()" + + # Non-unit step argument supplied. istep = int(step) if istep != step: raise ValueError, "non-integer step for randrange()" |