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