2.3.3 Comparisons

2.3.3 Comparisons

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:

Notes:

(1)

<> and != are alternate spellings for the same operator. != is the preferred spelling; <> is obsolescent.

Objects of different types, except different numeric types and different string 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. The <, <=, > and >= operators will raise a TypeError exception when any operand is a complex number.

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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Python Library Reference

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Release 2.4.4c1, documentation updated on 11 October 2006.