python学习day3--python基础

时间：2022-05-04 00:35:55

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

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