详解Python中的元组与逻辑运算符
Python元组
元组是另一个数据类型，类似于List（列表）。
元组用"()"标识。内部元素用逗号隔开。但是元素不能二次赋值，相当于只读列表。
#!/usr/bin/python # -*- coding: UTF-8 -*- tuple = ( 'abcd', 786 , 2.23, 'john', 70.2 ) tinytuple = (123, 'john') print tuple # 输出完整元组 print tuple[0] # 输出元组的第一个元素 print tuple[1:3] # 输出第二个至第三个的元素 print tuple[2:] # 输出从第三个开始至列表末尾的所有元素 print tinytuple * 2 # 输出元组两次 print tuple + tinytuple # 打印组合的元组
以上实例输出结果：
('abcd', 786, 2.23, 'john', 70.2)
abcd
(786, 2.23)
(2.23, 'john', 70.2)
(123, 'john', 123, 'john')
('abcd', 786, 2.23, 'john', 70.2, 123, 'john')
以下是元组无效的，因为元组是不允许更新的。而列表是允许更新的：
#!/usr/bin/python # -*- coding: UTF-8 -*- tuple = ( 'abcd', 786 , 2.23, 'john', 70.2 ) list = [ 'abcd', 786 , 2.23, 'john', 70.2 ] tuple[2] = 1000 # 元组中是非法应用 list[2] = 1000 # 列表中是合法应用
Python逻辑运算符
Python语言支持逻辑运算符，以下假设变量a为10，变量b为20：
以下实例演示了Python所有逻辑运算符的操作：
#!/usr/bin/python a = 10 b = 20 c = 0 if ( a and b ): print "Line 1 - a and b are true" else: print "Line 1 - Either a is not true or b is not true" if ( a or b ): print "Line 2 - Either a is true or b is true or both are true" else: print "Line 2 - Neither a is true nor b is true" a = 0 if ( a and b ): print "Line 3 - a and b are true" else: print "Line 3 - Either a is not true or b is not true" if ( a or b ): print "Line 4 - Either a is true or b is true or both are true" else: print "Line 4 - Neither a is true nor b is true" if not( a and b ): print "Line 5 - Either a is not true or b is not true or both are not true" else: print "Line 5 - a and b are true"
以上实例输出结果：
Line 1 - a and b are true Line 2 - Either a is true or b is true or both are true Line 3 - Either a is not true or b is not true Line 4 - Either a is true or b is true or both are true Line 5 - Either a is not true or b is not true or both are not true
