On 10/23/2014 04:47 PM, Alain Ketterlin wrote:
Simon Kennedy <sffjun...@gmail.com> writes:
Just out of academic interest, is there somewhere in the Python docs where the
following is explained?
3 == True
False
if 3:
print("It's Twue")
It's Twue
i.e. in the if statement 3 is True but not in the first
https://docs.python.org/2/reference/compound_stmts.html#the-if-statement
says: "The if statement [...] selects exactly one of the suites by
evaluating the expressions one by one until one is found to be true (see
section Boolean operations for the definition of true and false)"
Exactly, but in
if 3 == True:
the expression is 3==True , in which 3 and True compare unequal, thus,
the expression is false.
On the other hand, in
if 3:
the expression to evaluate is just the int object and the rules below apply.
and then:
https://docs.python.org/2/reference/expressions.html#booleans
says: "In the context of Boolean operations, and also when expressions
are used by control flow statements, the following values are
interpreted as false: False, None, numeric zero of all types, and empty
strings and containers (including strings, tuples, lists, dictionaries,
sets and frozensets). All other values are interpreted as true."
(links are to the 2.7 version of the reference manual, I think not much
has changed in 3.* versions.)
-- Alain.
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