3>0 is True

Peter Otten __peter__ at web.de
Wed Sep 15 14:46:07 CEST 2010


Yingjie Lan wrote:

> I am not sure how to interprete this, in the interactive mode:
> 
>>>> 3>0 is True
> False
>>>> (3>0) is True
> True
>>>> 3> (0 is True)
> True
> 
> Why did I get the first 'False'? I'm a little confused.

http://docs.python.org/reference/expressions.html#notin

"""
Unlike C, all comparison operations in Python have the same priority, which 
is lower than that of any arithmetic, shifting or bitwise operation. Also 
unlike C, expressions like a < b < c have the interpretation that is 
conventional in mathematics:

comparison    ::=  or_expr ( comp_operator or_expr )*
comp_operator ::=  "<" | ">" | "==" | ">=" | "<=" | "<>" | "!="
                   | "is" ["not"] | ["not"] "in"

Comparisons yield boolean values: True or False.
Comparisons can be chained arbitrarily, e.g., x < y <= z is equivalent to x 
< y and y <= z, except that y is evaluated only once (but in both cases z is 
not evaluated at all when x < y is found to be false).
"""

Peter



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