Mirror
/
cpython
mirror of https://github.com/python/cpython
4
1
Fork 0
Code Issues Releases Wiki Activity

Move error test to the function that needs it. Improve error message. (GH-30008)

This commit is contained in:
Raymond Hettinger 2021-12-09 20:24:50 -06:00 committed by GitHub
parent 50669083fe
commit 3fee7776e6
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 4 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
Lib/random.py
View File

@ -233,10 +233,8 @@ class Random(_random.Random):
break break
def _randbelow_with_getrandbits(self, n): def _randbelow_with_getrandbits(self, n):
"Return a random int in the range [0,n). Returns 0 if n==0." "Return a random int in the range [0,n). Defined for n > 0."
if not n:
return 0
getrandbits = self.getrandbits getrandbits = self.getrandbits
k = n.bit_length() # don't use (n-1) here because n can be 1 k = n.bit_length() # don't use (n-1) here because n can be 1
r = getrandbits(k) # 0 <= r < 2**k r = getrandbits(k) # 0 <= r < 2**k
@ -245,7 +243,7 @@ class Random(_random.Random):
return r return r
def _randbelow_without_getrandbits(self, n, maxsize=1<<BPF): def _randbelow_without_getrandbits(self, n, maxsize=1<<BPF):
"""Return a random int in the range [0,n). Returns 0 if n==0. """Return a random int in the range [0,n). Defined for n > 0.
The implementation does not use getrandbits, but only random. The implementation does not use getrandbits, but only random.
""" """
@ -256,8 +254,6 @@ class Random(_random.Random):
"enough bits to choose from a population range this large.\n" "enough bits to choose from a population range this large.\n"
"To remove the range limitation, add a getrandbits() method.") "To remove the range limitation, add a getrandbits() method.")
return _floor(random() * n) return _floor(random() * n)
if n == 0:
return 0
rem = maxsize % n rem = maxsize % n
limit = (maxsize - rem) / maxsize # int(limit * maxsize) % n == 0 limit = (maxsize - rem) / maxsize # int(limit * maxsize) % n == 0
r = random() r = random()
@ -338,7 +334,8 @@ class Random(_random.Random):
def choice(self, seq): def choice(self, seq):
"""Choose a random element from a non-empty sequence.""" """Choose a random element from a non-empty sequence."""
# raises IndexError if seq is empty if not seq:
raise IndexError('Cannot choose from an empty sequence')
return seq[self._randbelow(len(seq))] return seq[self._randbelow(len(seq))]
def shuffle(self, x): def shuffle(self, x):

4
Lib/test/test_random.py
View File

@ -816,10 +816,6 @@ class MersenneTwister_TestBasicOps(TestBasicOps, unittest.TestCase):
maxsize+1, maxsize=maxsize maxsize+1, maxsize=maxsize
) )
self.gen._randbelow_without_getrandbits(5640, maxsize=maxsize) self.gen._randbelow_without_getrandbits(5640, maxsize=maxsize)
# issue 33203: test that _randbelow returns zero on
# n == 0 also in its getrandbits-independent branch.
x = self.gen._randbelow_without_getrandbits(0, maxsize=maxsize)
self.assertEqual(x, 0)
# This might be going too far to test a single line, but because of our # This might be going too far to test a single line, but because of our
# noble aim of achieving 100% test coverage we need to write a case in # noble aim of achieving 100% test coverage we need to write a case in