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详解Python中的元组与逻辑运算符

网络编程 详解Python中的元组与逻辑运算符 06-22

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:
查看图片
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

Python中的字典与成员运算符初步探究
Python元字典字典(dictionary)是除列表以外python之中最灵活的内置数据结构类型。列表是有序的对象结合,字典是无序的对象集合。两者之间的区别在于:

举例讲解Python中的身份运算符的使用方法
Python身份运算符身份运算符用于比较两个对象的存储单元以下实例演示了Python所有身份运算符的操作:#!/usr/bin/pythona=20b=20if(aisb):print"Line1-aandbhavesameidenti

Python的条件语句与运算符优先级详解
Python条件语句Python条件语句是通过一条或多条语句的执行结果(True或者False)来决定执行的代码块。可以通过下图来简单了解条件语句的执行过程:Python


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标签:运算符,语句,列表,元素,字典