python学习笔记

一. 变量类型及其常见函数用法：数值型（int float complex） 字符串 (str） 列表 （list）元组 (tuple) 字典（dict）

• (1)数值

import math  a=20;b=3.2;   a**3；                                #结果为20*20*20《=》math.pow(20,3)  print(a**3);  print(round(100/3,3));                #小数点后面保留3位有效数字（保证输出格式）  print(math.ceil(3.32));               #向上取整  print(math.floor(3.32));              #向下取整  print(math.radians(180));             #度数转换成弧度制  divmod(10);                           #取商和余数  结果：8000  33.333   4   3  3.1415926   （3,1）

• (2)字符串

str="abc";str1="def"; print(a+b);                             #字符串拼接print(a*3);                             #字符串乘法结果：abcdef  abcabcabc

• （3）元组 （元组只要确定就不能修改 增加 删除任何元素）

  zoo=('wolf','dog','cat')   a,b,c=zoo                         #相当于a=zoo[0],b=zoo[1],c=zoo[2]   print("%s is 狼，%s is 狗,  %s is 猫"%(a,b,c))   print("{} is 狼，{} is 狗,  {} is 猫".format(a,b,c))   结果：wolf is 狼，dog is 狗，cat is 猫

  wolf is 狼，dog is 狗，cat is 猫

  %c 定制字符及其ASCLL码

%o 定制无符号八进制数

%x 定制无符号十六进制数

%d 定制整数

• (4)列表 类似于链表

  list_name=["car","jeep","bike"]     #创建列表list_name.append("tractor")         #在列表的末尾追加tractor元素list_name.insert(2,"train")         #在下标为2的位置插入train元素list_name.remove("jeep")            #删除list_name中的jeep元素list_name.pop()                     #弹出list_name的最后一个元素

列表的访问

list=["car","jeep",bike","tractor","airplane"]list[-2]                         # 访问倒数第二个元素 tractorprint(list[1,4])                 #输出标号为1,2,3的元素,及[jeep,bike,tractor]print(list[-3,-1])               #输出标号为-3，-2元素 及[bike,tractor]list1=["1","2"]list = list+list1                #list=["car","jeep",bike","tractor","airplane","1","2"]list1.extend(list)               # list1=["1","2","car","jeep",bike","tractor","airplane"]list2=["5","6"]list2 +=["7"]                    #list2=["5","6","7"]print(list)结果:     tractor          [jeep,bike,tractor]           [bike,tractor]          ["car","jeep",bike","tractor","airplane","1","2"]

常用列表方法

• (5)字典值

  • 字典键值对表示方法：dict = ["key1","value1","key2","value2" ...]

  • 字典的常用方法