Any object can be tested for truth value, for use in an if or while condition or as operand of the Boolean operations below. The following values are considered false:

1.None

2.False

3.zero of any numeric type, for example, 0, 0.0, 0j.

4.any empty sequence, for example, '', (), [].

5.any empty mapping, for example, {}.

6.instances of user-defined classes, if the class defines a __bool__() or __len__() method, when that method returns the integer zero or bool value False. [1]

All other values are considered true — so objects of many types are always true.

Operations and built-in functions that have a Boolean result always return 0 or False for false and 1 or True for true, unless otherwise stated. (Important exception: the Boolean operations or and and always return one of their operands.)

#在python中，任何对象都可以判断其真假值：True，False

#在if或while条件判断中，下面的情况值为False：

#

# 1.None

# 2.Flase

# 3.数值为0的情况，如：0,0.0,0j

# 4.所有空序列，如：'',(),[]

# 5.所有空mapping，如：{}

# 6.instances of user-defined classes, if the class defines a __bool__() or __len__() method,

#    when that method returns the integer zero or bool value False.

#

# All other values are considered true — so objects of many types are always true.

#

#

# 在运算操作和内建函数返回Boolean结果0或者Flase表示false

#1或True表示true

#

 print('x or y -> if x is false,then y, else x ')

 x, y = 2, 0

 print('{} or {} = {}'.format(x, y, x or y))

 x1, y1 = 0, 10

 print('{} or {} = {}'.format(x1, y1, x1 or y1))

 x2, y2 = 0, 0

 print('{} or {} = {}'.format(x2, y2, x2 or y2))

 print('#' * 50)

 print('x and y -> if x is false,then x, else y ')

 print('{} and {} = {}'.format(x, y, x and y))

 x1, y1 = 0, 10

 print('{} and {} = {}'.format(x1, y1, x1 and y1))

 x2, y2 = 0, 0

 print('{} and {} = {}'.format(x2, y2, x2 and y2))

 print('#' * 50)

 print('not x -> if x is false,then True,else False ')

 x = 2

 print('not {} = {}'.format(x, not x))

 x = 0

 print('not {} = {}'.format(x, not x))

Python 3.3.2 (v3.3.2:d047928ae3f6, May 16 2013, 00:03:43) [MSC v.1600 32 bit (Intel)] on win32

Type "copyright", "credits" or "license()" for more information.

>>> ================================ RESTART ================================

>>>

x or y -> if x is false,then y, else x

2 or 0 = 2

0 or 10 = 10

0 or 0 = 0

##################################################

x and y -> if x is false,then x, else y

2 and 0 = 0

0 and 10 = 0

0 and 0 = 0

##################################################

not x -> if x is false,then True,else False

not 2 = False

not 0 = True

>>>