Python Learning Day2 Notes

1. Use of the collection

Lists are ordered and can contain duplicate content.

A collection is unordered and cannot contain duplicate content.

1) Set Relationship test

#列表去重
list_1=[1,4,5,6,7,8,9,7,5,4,23,2] #有重复数据

List_1=set (list_1)
Print (List_1,type (list_1))

List_2=set ([2,6,0,44,55,3,4])
Print (list_1,list_2)

  #交集  
 Print (list_1.intersection (list_2)) 
 Print (List_1 & list_2) #不分先后顺序 
 
  #并集  
 Print (list_1.union (list_2)) 
 Print (list_1 | list_2) # In order of precedence 
 
  #差集  
 Print (list_1.difference (list_2)) #1里有2里没有 
 Print ( list_1-list_2) 
 Print (List_2.difference (list_1)) #2里有1里没有 
 Print (list_2-list_1) 
 
  #子集  
 List_3=set ([1,4,6]) 
 Print (List_3.issubset (list_1)) #3是否为1的子集 
 
  #父集  
 Print (List_1.issuperset (list_3)) #3是否为1的父集 
 
  #对称差集  
 Print (List_1.symmetric_difference (list_2)) 
 Print (list_1 ^ list_2) 
 
 # #1 and 2 No intersection returns true with intersection return false  
 Print (List_2.isdisjoint (list_1)) 
 
 2) basic Operations 
 

#添加
List_1.add (999) #单项
List_1.update ([111,112,113]) #多项

#修改
List_1.update ([2,3,4])

#删除
List_1.remove ("999") #删除不存在的值会报错
#随机删除
List_1.pop ()
#删除 Pass in a number
List_1.discard (#删除不存在的值不会报错)

#长度
Len (list_1)

#是不是成员
X in list_1  #列表 dictionary string to determine whether this is the case in a variable.

2. File operation

#读取
#data =open ("tudiword.py", encoding= "Utf-8"). Read ()

#文件保存为对象
F=open ("tudiword.py", encoding= "Utf-8") #文件句柄
Data=f.read ()
Data2=f.read ()

# Linux is sequentially output window under the order may be chaotic
Print (data)
Print (DATA2)

#写
#f. Write ("Lost train Band-the World of Tea") #提示错误 can't write

# Write needs to specify open mode
#r Read Mode W write mode does not write default to read mode
F=open ("tudiword.py", "R", encoding= "Utf-8")
F.close ()

# W Mode open file for Create file if previous file with the same name will overwrite
F1=open ("tudiword2.py", "W", encoding= "Utf-8")
F1.write ("The kindest time in life, \ r \ n")
F1.write ("as bright as water \ r \ n")

#读写都能进行的模式
#a = Append append does not overwrite the original file
F1=open ("tudiword2.py", "a", encoding= "Utf-8")
F1.write ("There are always people sitting around, \ r \ n")
F1.write ("stroking my withered shoulders \ r \ n")

#记得关闭
F1.close ()

Python Learning Day2 Notes