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。

 #命名列表
 name=["mark","jack","Tang long"]
 age=9
 #列表中可以放任何类型 ，也可以放变量
 name=["mark","jack","Tang long",22,age,56,22,47,88,9,5,6,7]
 #列表取值
 print("name-----",name)
 print("name[1]-----",name[1])
 print("name[-1]-----",name[-1])
 print("name[0:6]-----",name[0:6])
 print("name[:6]-----",name[:6])
 print("name[:6][2:4]---",name[:6][2:4])
 print("name[:6][2:4][0]---",name[:6][2:4][0])
 print("name[:6][2:4][0][1]---",name[:6][2:4][0][1])
 print("name[-5:-1]-----",name[-5:-1])
 print("name[-5:]-----",name[-5:])
 
 # 修改
 name[1]="Wangminghu"
 print("name====",name)
 #插入,一次只能插一个
 name.insert(2,"MingGou")
 print("name====",name)
 #追加
 name.append("Alex")
 print("name====",name)
 #删除
 name.remove("MingGou")
 print("name====",name)
 
 #运行结果
 name----- ['mark', 'jack', 'Tang long', 22, 9, 56, 22, 47, 88, 9, 5, 6, 7]
 name[1]----- jack
 name[-1]----- 7
 name[0:6]----- ['mark', 'jack', 'Tang long', 22, 9, 56]
 name[:6]----- ['mark', 'jack', 'Tang long', 22, 9, 56]
 name[:6][2:4]--- ['Tang long', 22]
 name[:6][2:4][0]--- Tang long
 name[:6][2:4][0][1]--- a
 name[-5:-1]----- [88, 9, 5, 6]
 name[-5:]----- [88, 9, 5, 6, 7]
 name==== ['mark', 'Wangminghu', 'Tang long', 22, 9, 56, 22, 47, 88, 9, 5, 6, 7]
 name==== ['mark', 'Wangminghu', 'MingGou', 'Tang long', 22, 9, 56, 22, 47, 88, 9, 5, 6, 7]
 name==== ['mark', 'Wangminghu', 'MingGou', 'Tang long', 22, 9, 56, 22, 47, 88, 9, 5, 6, 7, 'Alex']
 name==== ['mark', 'Wangminghu', 'Tang long', 22, 9, 56, 22, 47, 88, 9, 5, 6, 7, 'Alex']

列表使用

列表练习，打印结果前的数字为代码的行号：

 name=["Alex","jack","Rain","Eric","Monica","Fiona"]
 print('2 name====',name)
 #插入
 name.insert(-1,'MingHU')
 print('5 name===',name)
 name.insert(4,'MingLong')
 print('7 name===',name)
 #取值
 name2=name[2:7]
 print('10 name2===',name2)
 #删除
 name.remove('Fiona')
 print('13 name===',name)
 #连续删除用python的全局函数del删除内存的数据
 del name[4:6]
 print('16 name===',name)
 #del name 删除这个变量
 print('18 name===',name)
 name[4]="wangminglong(leader)"
 print('20 name===',name)
 #每隔一个取一个,最后一个数字为步长
 print('22 name===',name[0::2])#或者print('name===',name[::2])
 name=["Alex","jack","Rain",9,47,5,6,8,4,"Eric","Monica",9,6,9,4,5,"Fiona"]
 name3=['zhangsan','lisi','zhaoliu']
 #判断name中是否有9
 print(9 in name)
 if(9 in name):
     num_of_ele=name.count(9)#对9进行计数
     position_of_ele = name.index(9)#查找9的位置
     name[position_of_ele]=999
     print('31 [%s] 9 are/is in name,position [%s]'%(num_of_ele,position_of_ele))
     position_of_ele=name.index(9)
 print('33 name===',name)
 #改掉全部9
 for i in range(name.count(9)):
     ele_index=name.index(9)
     name[ele_index]=999
 print('38 name===',name)
 #将两个列表合起来用extend
 name.extend(name3)
 print('41 name===',name)
 #反转
 name.reverse();
 print('44 name===',name)
 #排序,python3之后数字和字符串不能一起排序，python2就可以
 print('46 name3===',name3)
 name3.sort()
 print('48 name3===',name3)
 #通过下标删除用pop方法
 name.pop()#默认删除最后一个
 print('51 name===',name)
 name.pop(3)
 print('53 name===',name)
 #复制一个列表
 #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
 #如果想完全克隆需import copy 模块用copy.deepcopy(name)
 name4=name.copy()
 print('58 name===',name)
 print('59 name4===',name4)
 
 运行结果：
 2 name==== ['Alex', 'jack', 'Rain', 'Eric', 'Monica', 'Fiona']
 5 name=== ['Alex', 'jack', 'Rain', 'Eric', 'Monica', 'MingHU', 'Fiona']
 7 name=== ['Alex', 'jack', 'Rain', 'Eric', 'MingLong', 'Monica', 'MingHU', 'Fiona']
 10 name2=== ['Rain', 'Eric', 'MingLong', 'Monica', 'MingHU']
 13 name=== ['Alex', 'jack', 'Rain', 'Eric', 'MingLong', 'Monica', 'MingHU']
 16 name=== ['Alex', 'jack', 'Rain', 'Eric', 'MingHU']
 18 name=== ['Alex', 'jack', 'Rain', 'Eric', 'MingHU']
 20 name=== ['Alex', 'jack', 'Rain', 'Eric', 'wangminglong(leader)']
 22 name=== ['Alex', 'Rain', 'wangminglong(leader)']
 True
 31 [3] 9 are/is in name,position [3]
 33 name=== ['Alex', 'jack', 'Rain', 999, 47, 5, 6, 8, 4, 'Eric', 'Monica', 9, 6, 9, 4, 5, 'Fiona']
 38 name=== ['Alex', 'jack', 'Rain', 999, 47, 5, 6, 8, 4, 'Eric', 'Monica', 999, 6, 999, 4, 5, 'Fiona']
 41 name=== ['Alex', 'jack', 'Rain', 999, 47, 5, 6, 8, 4, 'Eric', 'Monica', 999, 6, 999, 4, 5, 'Fiona', 'zhangsan', 'lisi', 'zhaoliu']
 44 name=== ['zhaoliu', 'lisi', 'zhangsan', 'Fiona', 5, 4, 999, 6, 999, 'Monica', 'Eric', 4, 8, 6, 5, 47, 999, 'Rain', 'jack', 'Alex']
 46 name3=== ['zhangsan', 'lisi', 'zhaoliu']
 48 name3=== ['lisi', 'zhangsan', 'zhaoliu']
 51 name=== ['zhaoliu', 'lisi', 'zhangsan', 'Fiona', 5, 4, 999, 6, 999, 'Monica', 'Eric', 4, 8, 6, 5, 47, 999, 'Rain', 'jack']
 53 name=== ['zhaoliu', 'lisi', 'zhangsan', 5, 4, 999, 6, 999, 'Monica', 'Eric', 4, 8, 6, 5, 47, 999, 'Rain', 'jack']
 58 name=== ['zhaoliu', 'lisi', 'zhangsan', 5, 4, 999, 6, 999, 'Monica', 'Eric', 4, 8, 6, 5, 47, 999, 'Rain', 'jack']
 59 name4=== ['zhaoliu', 'lisi', 'zhangsan', 5, 4, 999, 6, 999, 'Monica', 'Eric', 4, 8, 6, 5, 47, 999, 'Rain', 'jack']

列表练习

4.查看长度用len()函数，适用于字符串，列表等等