后端开发|Python教程
Python,元组,逻辑运算符
后端开发-Python教程
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。
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#!/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
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以上实例输出结果：
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(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/pythona = 10b = 20c = 0if ( 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 = 0if ( 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 trueLine 2 - Either a is true or b is true or both are trueLine 3 - Either a is not true or b is not trueLine 4 - Either a is true or b is true or both are trueLine 5 - Either a is not true or b is not true or both are not true
