To reproduce:
In [1]: from hypothesis import strategies as st
In [2]: bool_st = st.booleans()
In [3]: all(bool_st.example() for _ in range(1000))
Out[3]: True
Why does st.booleans().example() always return True? My understanding is that the example method should return examples of what could be output by a strategy and does so somewhat at random.
Relatedly, st.sampled_from(...) seems to never return the first item in the iterable:
In [1]: from hypothesis import strategies as st
In [2]: from collections import Counter
In [3]: samp_st = st.sampled_from(list(range(10)))
In [4]: examples = [samp_st.example() for _ in range(1000)]
In [5]: cnt = Counter(examples)
In [6]: cnt.most_common()
Out[6]: [(1, 512), (2, 282), (3, 119), (4, 55), (5, 22), (6, 5), (7, 4), (8, 1)]
So what's going on here?
I'm aware that the example method documentation says the method "shouldn't be taken too seriously" (see here). But this offers very little in the way of explanation and it would be nice to get more insight into why this is happening.
Simple: the .example() method avoids showing the simplest possible example from a strategy, because that example is usually trivial. Admittedly this is less useful for st.booleans().example(), but that's why!
For your comments, lists(...).example() keeps producing the empty list due to a limitation in our uniqueness detection - see issues 1864, 1982, and PR 1961 for more details; we'll fix it as soon as we have a good way to do so.
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