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Code Issues Projects Releases Packages Wiki Activity Actions 8

Fulfill Martin's request to use try/except rather than a "look before

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you leap" approach.  Makes the early call to os.urandom() unnecessary.
This commit is contained in:
Raymond Hettinger 2004-09-05 00:00:42 +00:00
parent c4536a1dea
commit c1c43cad63
2 changed files with 13 additions and 18 deletions
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25
Lib/random.py
View file

@ -44,6 +44,8 @@ from types import MethodType as _MethodType, BuiltinMethodType as _BuiltinMethod
from math import log as _log, exp as _exp, pi as _pi, e as _e 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 sqrt as _sqrt, acos as _acos, cos as _cos, sin as _sin
from math import floor as _floor from math import floor as _floor
from os import urandom as _urandom
from binascii import hexlify as _hexlify
__all__ = ["Random","seed","random","uniform","randint","choice","sample", __all__ = ["Random","seed","random","uniform","randint","choice","sample",
"randrange","shuffle","normalvariate","lognormvariate", "randrange","shuffle","normalvariate","lognormvariate",
@ -59,13 +61,6 @@ SG_MAGICCONST = 1.0 + _log(4.5)
BPF = 53 # Number of bits in a float BPF = 53 # Number of bits in a float
RECIP_BPF = 2**-BPF RECIP_BPF = 2**-BPF
try:
from os import urandom as _urandom
from binascii import hexlify as _hexlify
_urandom(1) # verify that urandom is implemented
except (ImportError, NotImplementedError):
_urandom = None
# Translated by Guido van Rossum from C source provided by # Translated by Guido van Rossum from C source provided by
# Adrian Baddeley. Adapted by Raymond Hettinger for use with # Adrian Baddeley. Adapted by Raymond Hettinger for use with
@ -111,11 +106,11 @@ class Random(_random.Random):
""" """
if a is None: if a is None:
if _urandom is None: try:
a = long(_hexlify(_urandom(16)), 16)
except NotImplementedError:
import time import time
a = long(time.time() * 256) # use fractional seconds a = long(time.time() * 256) # use fractional seconds
else:
a = long(_hexlify(_urandom(16)), 16)
super(Random, self).seed(a) super(Random, self).seed(a)
self.gauss_next = None self.gauss_next = None
@ -620,11 +615,11 @@ class WichmannHill(Random):
""" """
if a is None: if a is None:
if _urandom is None: try:
a = long(_hexlify(_urandom(16)), 16)
except NotImplementedError:
import time import time
a = long(time.time() * 256) # use fractional seconds a = long(time.time() * 256) # use fractional seconds
else:
a = long(_hexlify(_urandom(16)), 16)
if not isinstance(a, (int, long)): if not isinstance(a, (int, long)):
a = hash(a) a = hash(a)
@ -759,14 +754,10 @@ class HardwareRandom(Random):
def random(self): def random(self):
"""Get the next random number in the range [0.0, 1.0).""" """Get the next random number in the range [0.0, 1.0)."""
if _urandom is None:
raise NotImplementedError('Cannot find hardware entropy source')
return (long(_hexlify(_urandom(7)), 16) >> 3) * RECIP_BPF return (long(_hexlify(_urandom(7)), 16) >> 3) * RECIP_BPF
def getrandbits(self, k): def getrandbits(self, k):
"""getrandbits(k) -> x. Generates a long int with k random bits.""" """getrandbits(k) -> x. Generates a long int with k random bits."""
if _urandom is None:
raise NotImplementedError('Cannot find hardware entropy source')
if k <= 0: if k <= 0:
raise ValueError('number of bits must be greater than zero') raise ValueError('number of bits must be greater than zero')
if k != int(k): if k != int(k):

6
Lib/test/test_random.py
View file

@ -495,7 +495,11 @@ def test_main(verbose=None):
TestDistributions, TestDistributions,
TestModule] TestModule]
if random._urandom is not None: try:
random.HardwareRandom().random()
except NotImplementedError:
pass
else:
testclasses.append(HardwareRandom_TestBasicOps) testclasses.append(HardwareRandom_TestBasicOps)
test_support.run_unittest(*testclasses) test_support.run_unittest(*testclasses)