python开发_python中的Boolean运算和真假值
|
python中的真假值： Any object can be tested truth value, use an condition 1.None2.False 3.zero of any numeric type,<span style="color: #0000ff;">for example,0.0<span style="color: #000000;">,0j. 4.any empty sequence,<span style="color: #800000;">''<span style="color: #000000;">,(),[]. 5.any empty mapping,<span style="color: #0000ff;">for<span style="color: #000000;"> example,{}. 6.instances of user-defined classes,<span style="color: #0000ff;">if the <span style="color: #0000ff;">class defines a <span style="color: #800080;">bool() <span style="color: #0000ff;">or <span style="color: #800080;">len() method,when that method returns the integer zero <span style="color: #0000ff;">or bool value False. [1<span style="color: #000000;">] All other values are considered true — so objects of many types are always true. Operations <span style="color: #0000ff;">and built-<span style="color: #0000ff;">in functions that have a Boolean result always <span style="color: #0000ff;">return 0 <span style="color: #0000ff;">or False <span style="color: #0000ff;">for false <span style="color: #0000ff;">and 1 <span style="color: #0000ff;">or True <span style="color: #0000ff;">for true,unless otherwise stated. (Important exception: the Boolean operations <span style="color: #0000ff;">or <span style="color: #0000ff;">and <span style="color: #0000ff;">and always <span style="color: #0000ff;">return one of their operands.) 总结： ( if x is false,then y,else x x,y = 2 (.format(x,y,x x1,y1 = 0,10 (.format(x1,y1,x1 x2,y2 = (.format(x2,y2,x2 ( * 50 ( if x is false,then x,else y (.format(x,x x1,10 (.format(x1,x1 x2,0 (.format(x2,x2 ( * 50 ( if x is false,then True,else False x = 2 (.format(x, x = (.format(x, x)) Python 3.3.2 (v3.3.2:d047928ae3f6,May 16 2013,00:03:43) [MSC v.1600 32, >>> ================================ RESTART ================================ >>> y -> x false,2 0 = 2 10 = 10 0 = x y -> x false,2 0 = 10 = 0 = x -> x false, 2 = 0 =>>>（编辑：安卓应用网） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |