Python Pocket Reference, 3rd Edition

Built-in Types and Operators

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7

Operations by Category

All built-in types support the comparisons and Boolean oper-

ations listed in Table 2.

Boolean

true means any nonzero number or any nonempty

collection object (list, dictionary, etc.). The names

True and

False are pre-assigned to true and false values and behave

like integers 1 and 0. The special object

None is false.

Comparisons return

True or False and are applied recur-

sively in compound objects as needed to determine a result.

Boolean

and and or operators stop (short-circuit) as soon as a

result is known and return one of the two operand objects

(on left or right).

a

Comparison operators can be chained: x<y<zis similar to x<yandy<z, except that

y is evaluated only once in the first format.

b

Floor division (X//Y), new in Python Version 2.2, always truncates fractional remainders.

Classic division (X/Y) truncates integer divisionresults inVersion 2.2but willbe changedto true

division (always keeping remainders) in Version 3.0. In Version 2.2 and later, use from __

future__ import division

to make the / operator return a true division result (e.g., 1/2 is

0.5).

c

In Python 2.4, expressions in parentheses can also be generator expressions, which are similar to list

comprehensions but produce a series of values on demand in iteration contexts.

d

List literals in square brackets ([...]) can be a simple list of expressions, or a list comprehension;

see the ...