On 2013-06-14 10:50, Nick the Gr33k wrote:
I started another thread because the last one was !@#$'ed up by irrelevant
replies and was difficult to jeep track.
>>> name="abcd"
>>> month="efgh"
>>> year="ijkl"
>>> print(name or month or year)
abcd
Can understand that, it takes the first string out of the 3 strings that has a
truthy value.
>>> print("k" in (name and month and year))
True
No clue. since the expression in parenthesis returns 'abcd' how can 'k'
contained within 'abcd' ?
>>> print(name and month and year)
ijkl
Seems here is returning the last string out of 3 strings, but have no clue why
Python doing this.
>>> print("k" in (name and month and year))
True
>>>
yes, since expression returns 'ijkl', then the in operator can detect the 'k'
character within the returned string.
This is all iw ant to know.
This is all you need to read:
http://docs.python.org/2/reference/expressions.html#boolean-operations
Note the difference between how "or" and "and" each short-circuit. That is why
the (name or month or year) returns the first truthy value while (name and month
and year) returns the last truthy value. When "or" finds the first truthy value,
it can stop looking since the whole expression must be truthy no matter what the
values are after it. "and" cannot stop looking until it finds a falsy value or
runs out of values to look at.
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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