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Small clean-ups.

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This commit is contained in:
Raymond Hettinger 2010-09-07 09:32:57 +00:00
parent e572bcec78
commit c324697bac
1 changed files with 12 additions and 29 deletions
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41
Lib/random.py
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@ -167,7 +167,7 @@ def randrange(self, start, stop=None, step=1, int=int):
This fixes the problem with randint() which includes the This fixes the problem with randint() which includes the
endpoint; in Python this is usually not what you want. endpoint; in Python this is usually not what you want.
Do not supply the 'int' and 'maxwidth' arguments. Do not supply the 'int' argument.
""" """
# This code is a bit messy to make it fast for the # This code is a bit messy to make it fast for the
@ -186,20 +186,7 @@ def randrange(self, start, stop=None, step=1, int=int):
raise ValueError("non-integer stop for randrange()") raise ValueError("non-integer stop for randrange()")
width = istop - istart width = istop - istart
if step == 1 and width > 0: if step == 1 and width > 0:
# Note that return istart + self._randbelow(width)
# int(istart + self.random()*width)
# instead would be incorrect. For example, consider istart
# = -2 and istop = 0. Then the guts would be in
# -2.0 to 0.0 exclusive on both ends (ignoring that random()
# might return 0.0), and because int() truncates toward 0, the
# final result would be -1 or 0 (instead of -2 or -1).
# istart + int(self.random()*width)
# would also be incorrect, for a subtler reason: the RHS
# can return a long, and then randrange() would also return
# a long, but we're supposed to return an int (for backward
# compatibility).
return int(istart + self._randbelow(width))
if step == 1: if step == 1:
raise ValueError("empty range for randrange() (%d,%d, %d)" % (istart, istop, width)) raise ValueError("empty range for randrange() (%d,%d, %d)" % (istart, istop, width))
@ -233,20 +220,16 @@ def _randbelow(self, n, int=int, _maxwidth=1<<BPF, type=type,
by a single call to the underlying generator. by a single call to the underlying generator.
""" """
try: getrandbits = self.getrandbits
getrandbits = self.getrandbits # Only call self.getrandbits if the original random() builtin method
except AttributeError: # has not been overridden or if a new getrandbits() was supplied.
pass # This assures that the two methods correspond.
else: if type(self.random) is _BuiltinMethod or type(getrandbits) is _Method:
# Only call self.getrandbits if the original random() builtin method k = n.bit_length() # don't use (n-1) here because n can be 1
# has not been overridden or if a new getrandbits() was supplied. r = getrandbits(k) # 0 <= r < 2**k
# This assures that the two methods correspond. while r >= n:
if type(self.random) is _BuiltinMethod or type(getrandbits) is _Method: r = getrandbits(k)
k = n.bit_length() # don't use (n-1) here because n can be 1 return r
r = getrandbits(k) # 0 <= r < 2**k
while r >= n:
r = getrandbits(k)
return r
if n >= _maxwidth: if n >= _maxwidth:
_warn("Underlying random() generator does not supply \n" _warn("Underlying random() generator does not supply \n"
"enough bits to choose from a population range this large") "enough bits to choose from a population range this large")