[Python-checkins] Move error test to the function that needs it. Improve error message. (GH-30008)
rhettinger
webhook-mailer at python.org
Thu Dec 9 21:24:59 EST 2021
https://github.com/python/cpython/commit/3fee7776e6ed8ab023a0220da1daf3160fda868b
commit: 3fee7776e6ed8ab023a0220da1daf3160fda868b
branch: main
author: Raymond Hettinger <rhettinger at users.noreply.github.com>
committer: rhettinger <rhettinger at users.noreply.github.com>
date: 2021-12-09T20:24:50-06:00
summary:
Move error test to the function that needs it. Improve error message. (GH-30008)
files:
M Lib/random.py
M Lib/test/test_random.py
diff --git a/Lib/random.py b/Lib/random.py
index 92a71e14c480b..e8bc9416fcd94 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -233,10 +233,8 @@ def __init_subclass__(cls, /, **kwargs):
break
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
k = n.bit_length() # don't use (n-1) here because n can be 1
r = getrandbits(k) # 0 <= r < 2**k
@@ -245,7 +243,7 @@ def _randbelow_with_getrandbits(self, n):
return r
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.
"""
@@ -256,8 +254,6 @@ def _randbelow_without_getrandbits(self, n, maxsize=1<<BPF):
"enough bits to choose from a population range this large.\n"
"To remove the range limitation, add a getrandbits() method.")
return _floor(random() * n)
- if n == 0:
- return 0
rem = maxsize % n
limit = (maxsize - rem) / maxsize # int(limit * maxsize) % n == 0
r = random()
@@ -338,7 +334,8 @@ def randint(self, a, b):
def choice(self, seq):
"""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))]
def shuffle(self, x):
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
index cdae8897c2ae2..b80aeca26cf48 100644
--- a/Lib/test/test_random.py
+++ b/Lib/test/test_random.py
@@ -816,10 +816,6 @@ def test_randbelow_without_getrandbits(self):
maxsize+1, 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
# noble aim of achieving 100% test coverage we need to write a case in
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