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The documentation for random.uniform says that random.uniform(a,b) 
should return a number strictly less than b, assuming a<b. (The result 
should be strictly less than a if a>b.) Thus both of the following 
expressions should always evaluate to False:
a<b and b in [random.uniform(a,b) for i in range(20)]
a<b and b in [random.uniform(b,a) for i in range(20)]
Yet both of them evaluate to True (except, presumably, one time in a 
million) after doing the following assignments:
a = 1.0
b = 1.0 + 2.0**-52
Other values of a and b also exist for which random.uniform will 
sometimes return its upper limit. (For example, the -52 can be 
increased to -51, -50, etc., with correspondingly less frequent 
violations of the spec.)
Because this is a case where the code is violating an explicit 
specification in the documentation, I'm reporting it as a behavior bug. 
But perhaps the behavior is as intended and the documentation is at 
fault. For that reason, I'm also emailing docs@python.org.
 
The documentation would in any case need a little touching up, in that 
it has a self-contradictory specification for the case where a=b. There 
is no value N for which a<=N<b, given a=b. That minor touch-up could be 
combined with allowing the behavior described in this bug report, if 
that behavior is in fact desired.

The distinction between < and <= is fairly meaningless when applied to a 
computed floating-point result. I think the docs should be fixed to 
replace the < with <=. In any case, the b <= N < a bit has the 
inequalities the wrong way around: presumably it was intended to read b < 
N <= a. The docs for random.triangular should also be fixed in the same 
way.
(N.B. What *is* always true is that the result of random.random() is never 
1.0. And that's a useful property---without it, random.uniform(a, b) can 
even return values *outside* the closed interval [a, b].)
To me, it doesn't seem worth slowing down random.uniform itself with extra 
checks: it's the sort of function that often gets called millions of times 
within a simulation, or numerical algorithm (e.g. Monte-Carlo 
integration), and it's trivial for the user to add his or her own check if 
necessary.
I also think it's a nice property that random.uniform currently degrades 
gracefully when a == b, producing the expected point distribution at a. I 
wouldn't want to change that.
So: +1 for amending the docs. -1 for changing random.uniform.

Doc update

Thanks, applied in r68724.