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Python Library Reference |  |
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Python Library Reference | |
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Comparison operations are supported by all objects. They all have the
same priority (which is higher than that of the Boolean operations).
Comparisons can be chained arbitrarily; for example, 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).
This table summarizes the comparison operations:
| Operation | Meaning | Notes |
|---|---|---|
< |
strictly less than | |
<= |
less than or equal | |
> |
strictly greater than | |
>= |
greater than or equal | |
== |
equal | |
!= |
not equal | (1) |
<> |
not equal | (1) |
is |
object identity | |
is not |
negated object identity |
Notes:
<> and != are alternate spellings for the same operator.
(I couldn't choose between ABC and C! :-)
!= is the preferred spelling; <> is obsolescent.
Objects of different types, except different numeric types, never compare equal; such objects are ordered consistently but arbitrarily (so that sorting a heterogeneous array yields a consistent result). Furthermore, some types (for example, file objects) support only a degenerate notion of comparison where any two objects of that type are unequal. Again, such objects are ordered arbitrarily but consistently.
Instances of a class normally compare as non-equal unless the class defines the __cmp__() method. Refer to the Python Reference Manual for information on the use of this method to effect object comparisons.
Implementation note: Objects of different types except numbers are ordered by their type names; objects of the same types that don't support proper comparison are ordered by their address.
Two more operations with the same syntactic priority, "in" and "not in" , are supported only by sequence types (below).
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