python学习day3--python基础
1.python不用声明变量的类型，运行时python自己进行判断
2.尽量不要用“+”去拼接字符串，运行时会每遇到一个“+”就开辟一块内存空间，使用如下方式进行字符串的拼接。
msg=''' information of user %s ----------------------- name: %s age : %d job : %s -----------end--------- '''%(name,name,age,job) print(msg)
3.列表的语法和练习
python中叫列表，在其它语言中叫数组。
1 #命名列表 2 name=["mark","jack","Tang long"] 3 age=9 4 #列表中可以放任何类型 ，也可以放变量 5 name=["mark","jack","Tang long",22,age,56,22,47,88,9,5,6,7] 6 #列表取值 7 print("name-----",name) 8 print("name[1]-----",name[1]) 9 print("name[-1]-----",name[-1]) 10 print("name[0:6]-----",name[0:6]) 11 print("name[:6]-----",name[:6]) 12 print("name[:6][2:4]---",name[:6][2:4]) 13 print("name[:6][2:4][0]---",name[:6][2:4][0]) 14 print("name[:6][2:4][0][1]---",name[:6][2:4][0][1]) 15 print("name[-5:-1]-----",name[-5:-1]) 16 print("name[-5:]-----",name[-5:]) 17 18 # 修改 19 name[1]="Wangminghu" 20 print("name====",name) 21 #插入,一次只能插一个 22 name.insert(2,"MingGou") 23 print("name====",name) 24 #追加 25 name.append("Alex") 26 print("name====",name) 27 #删除 28 name.remove("MingGou") 29 print("name====",name) 30 31 #运行结果 32 name----- ['mark', 'jack', 'Tang long', 22, 9, 56, 22, 47, 88, 9, 5, 6, 7] 33 name[1]----- jack 34 name[-1]----- 7 35 name[0:6]----- ['mark', 'jack', 'Tang long', 22, 9, 56] 36 name[:6]----- ['mark', 'jack', 'Tang long', 22, 9, 56] 37 name[:6][2:4]--- ['Tang long', 22] 38 name[:6][2:4][0]--- Tang long 39 name[:6][2:4][0][1]--- a 40 name[-5:-1]----- [88, 9, 5, 6] 41 name[-5:]----- [88, 9, 5, 6, 7] 42 name==== ['mark', 'Wangminghu', 'Tang long', 22, 9, 56, 22, 47, 88, 9, 5, 6, 7] 43 name==== ['mark', 'Wangminghu', 'MingGou', 'Tang long', 22, 9, 56, 22, 47, 88, 9, 5, 6, 7] 44 name==== ['mark', 'Wangminghu', 'MingGou', 'Tang long', 22, 9, 56, 22, 47, 88, 9, 5, 6, 7, 'Alex'] 45 name==== ['mark', 'Wangminghu', 'Tang long', 22, 9, 56, 22, 47, 88, 9, 5, 6, 7, 'Alex']
列表练习，打印结果前的数字为代码的行号：
1 name=["Alex","jack","Rain","Eric","Monica","Fiona"] 2 print('2 name====',name) 3 #插入 4 name.insert(-1,'MingHU') 5 print('5 name===',name) 6 name.insert(4,'MingLong') 7 print('7 name===',name) 8 #取值 9 name2=name[2:7] 10 print('10 name2===',name2) 11 #删除 12 name.remove('Fiona') 13 print('13 name===',name) 14 #连续删除用python的全局函数del删除内存的数据 15 del name[4:6] 16 print('16 name===',name) 17 #del name 删除这个变量 18 print('18 name===',name) 19 name[4]="wangminglong(leader)" 20 print('20 name===',name) 21 #每隔一个取一个,最后一个数字为步长 22 print('22 name===',name[0::2])#或者print('name===',name[::2]) 23 name=["Alex","jack","Rain",9,47,5,6,8,4,"Eric","Monica",9,6,9,4,5,"Fiona"] 24 name3=['zhangsan','lisi','zhaoliu'] 25 #判断name中是否有9 26 print(9 in name) 27 if(9 in name): 28 num_of_ele=name.count(9)#对9进行计数 29 position_of_ele = name.index(9)#查找9的位置 30 name[position_of_ele]=999 31 print('31 [%s] 9 are/is in name,position [%s]'%(num_of_ele,position_of_ele)) 32 position_of_ele=name.index(9) 33 print('33 name===',name) 34 #改掉全部9 35 for i in range(name.count(9)): 36 ele_index=name.index(9) 37 name[ele_index]=999 38 print('38 name===',name) 39 #将两个列表合起来用extend 40 name.extend(name3) 41 print('41 name===',name) 42 #反转 43 name.reverse(); 44 print('44 name===',name) 45 #排序,python3之后数字和字符串不能一起排序，python2就可以 46 print('46 name3===',name3) 47 name3.sort() 48 print('48 name3===',name3) 49 #通过下标删除用pop方法 50 name.pop()#默认删除最后一个 51 print('51 name===',name) 52 name.pop(3) 53 print('53 name===',name) 54 #复制一个列表 55 #列表里可以嵌列表,如果列表中嵌了列表，在普通copy时，嵌入的列表只复制内存地址,两个列表中任何一个嵌入的列表修改，另外一个都跟着修改 56 #如果想完全克隆需import copy 模块用copy.deepcopy(name) 57 name4=name.copy() 58 print('58 name===',name) 59 print('59 name4===',name4) 60 61 运行结果： 62 2 name==== ['Alex', 'jack', 'Rain', 'Eric', 'Monica', 'Fiona'] 63 5 name=== ['Alex', 'jack', 'Rain', 'Eric', 'Monica', 'MingHU', 'Fiona'] 64 7 name=== ['Alex', 'jack', 'Rain', 'Eric', 'MingLong', 'Monica', 'MingHU', 'Fiona'] 65 10 name2=== ['Rain', 'Eric', 'MingLong', 'Monica', 'MingHU'] 66 13 name=== ['Alex', 'jack', 'Rain', 'Eric', 'MingLong', 'Monica', 'MingHU'] 67 16 name=== ['Alex', 'jack', 'Rain', 'Eric', 'MingHU'] 68 18 name=== ['Alex', 'jack', 'Rain', 'Eric', 'MingHU'] 69 20 name=== ['Alex', 'jack', 'Rain', 'Eric', 'wangminglong(leader)'] 70 22 name=== ['Alex', 'Rain', 'wangminglong(leader)'] 71 True 72 31 [3] 9 are/is in name,position [3] 73 33 name=== ['Alex', 'jack', 'Rain', 999, 47, 5, 6, 8, 4, 'Eric', 'Monica', 9, 6, 9, 4, 5, 'Fiona'] 74 38 name=== ['Alex', 'jack', 'Rain', 999, 47, 5, 6, 8, 4, 'Eric', 'Monica', 999, 6, 999, 4, 5, 'Fiona'] 75 41 name=== ['Alex', 'jack', 'Rain', 999, 47, 5, 6, 8, 4, 'Eric', 'Monica', 999, 6, 999, 4, 5, 'Fiona', 'zhangsan', 'lisi', 'zhaoliu'] 76 44 name=== ['zhaoliu', 'lisi', 'zhangsan', 'Fiona', 5, 4, 999, 6, 999, 'Monica', 'Eric', 4, 8, 6, 5, 47, 999, 'Rain', 'jack', 'Alex'] 77 46 name3=== ['zhangsan', 'lisi', 'zhaoliu'] 78 48 name3=== ['lisi', 'zhangsan', 'zhaoliu'] 79 51 name=== ['zhaoliu', 'lisi', 'zhangsan', 'Fiona', 5, 4, 999, 6, 999, 'Monica', 'Eric', 4, 8, 6, 5, 47, 999, 'Rain', 'jack'] 80 53 name=== ['zhaoliu', 'lisi', 'zhangsan', 5, 4, 999, 6, 999, 'Monica', 'Eric', 4, 8, 6, 5, 47, 999, 'Rain', 'jack'] 81 58 name=== ['zhaoliu', 'lisi', 'zhangsan', 5, 4, 999, 6, 999, 'Monica', 'Eric', 4, 8, 6, 5, 47, 999, 'Rain', 'jack'] 82 59 name4=== ['zhaoliu', 'lisi', 'zhangsan', 5, 4, 999, 6, 999, 'Monica', 'Eric', 4, 8, 6, 5, 47, 999, 'Rain', 'jack']
4.查看长度用len()函数，适用于字符串，列表等等
