Boolean operations have the lowest priority of all Python operations:
condition: or_test | lambda_form or_test: and_test | or_test "or" and_test and_test: not_test | and_test "and" not_test not_test: comparison | "not" not_test lambda_form: "lambda" [parameter_list]: condition
In the context of Boolean operations, and also when conditions are
used by control flow statements, the following values are interpreted
as false: None, numeric zero of all types, empty sequences
(strings, tuples and lists), and empty mappings (dictionaries). All
other values are interpreted as true.
The operator not yields 1 if its argument is false, 0 otherwise.
The condition x and y first evaluates x; if
x is false, its value is returned; otherwise, y is
evaluated and the resulting value is returned.
The condition x or y first evaluates x; if
x is true, its value is returned; otherwise, y is
evaluated and the resulting value is returned.
(Note that and and or do not restrict the value and type
they return to 0 and 1, but rather return the last evaluated argument.
This is sometimes useful, e.g. if s is a string that should be
replaced by a default value if it is empty, the expression
s or 'foo' yields the desired value. Because not has to
invent a value anyway, it does not bother to return a value of the
same type as its argument, so e.g. not 'foo' yields 0,
not ''.)
Lambda forms (lambda expressions) have the same syntactic position as
conditions. They are a shorthand to create anonymous functions; the
expression lambda arguments: condition
yields a function object that behaves virtually identical to one
defined with
def name (arguments): return condition.
See section 
for the syntax of
parameter lists. Note that functions created with lambda forms cannot
contain statements.