2016/12/30_python

Today's main learning content:

Python:

1. Use of dictionaries

1) How to create a dictionary

Dicts = {"Name": "Juncx", "Age": 17}

Dicts = Dict ("Name:juncx", "age:17")

2) operation of the dictionary

Print (dicts["name"]) #取出 value corresponding to "name" key

dicts["name"] = "June" #对 the value corresponding to the "name" key is modified; If this key is not present, add

Del dicts["name"] #用Python中通用的del方法删除dicts字典的 "name" Key and value

Dicts.pop ("name") #删除

Dicts.popitem () #随机删除

Print (dicts["name"]) #如果键不存在则会报KeyError

Print (Dicts.get ("name")) #效果同上, but will not report Keyerror

Print (name in dicts) #判断 "name" Whether the Dicts dictionary has a "name" key if there is a return true

Print (Dict.items ()) #把dicts字典转换为列表

3) traversing the dictionary

For I in Dicts:for Key,value in Dicts.items ():

Print (I,dicts[i]) print (key,value)

"' The first traversal dictionary is more efficient than the second traversal dictionary"

2, the use of the collection

1) How to create a collection

set = Set ([1,3,5,7,9]) #创建一个集合

LIST_01 = [2,4,6,8,3] #创建一个列表

list_02 = [2,3,2,6,8,2] #创建一个列表

list_01 = Set (list_01) result:{2,4,6,8,3}

list_02 = Set (list_02) reuslt:{2,3,6,8} #在列表转换为集合时, the duplicate value is removed and the same value is never present in the collection

2) Multi-collection operation

Print (list_01 & list_02) #交集用符号: "&"

Print (list_01 | list_02) #并集用符号: "|"

Print (list_01-list_02) #差集用符号: "-"

Print (list_01 ^ list_02) #对称差集用符号: "^"

Print (List_01.intersection (list_02)) #交集

Print (List_01.union (list_02)) #并集

Print (List_01.difference (list_02)) #差集

Print (List_01.symmetric_difference (list_02)) #对称差集

Print (List_01.issubset (list_02)) #判断list_01是否是list_02的子集

Print (List_01.issuperset (list_02)) #判断list_01是否是list_02的父集

Print (List_01.isdisjoint (list_02)) #判断list_01与list_02是否有相同的值

3) operation of single set

List_01.add (999) #对list_01添加一个数据项

List_01.update ([101,102,103]) #对list_01添加一组数据项

List_01.remove (101) #移除指定项, error if not present

List_01.discard (101) #移除指定项, no error

List_01.pop () #移除随机项

"In" and "not" operations (same dictionary)

3. File Operation 01

1) Process of file operation

Open the file first, then manipulate the file, and then close the file

File = Open ("Demo.txt", "R", encoding= "Utf-8") #第一个参数是指定文件夹, the second parameter is the action to be performed ("R": Read, "W": Write, "A": Append, "B": binary), Encoding specifying the encoding format

data = File.read () print (data) #读取txt文件的全部内容并打印在屏幕上

Print (File.readline ()) #读取txt文件的一行内容打印在屏幕上

File.write ("I love Python") #写入字符到demo. txt file, overwriting the original text if it is not in append mode

File.close () #关闭连接

2) file deletion and modification

Print (File.tell ()) #显示文件内容指针所在的位置

File.seek (0) #设置文件内容指针的位置为0

File.flush () #刷新缓存

4. Progress bar

Import Sys,time

For I in range (50):

Sys.stdout.write ("#")

Sys.stdout.flush ()

Time.sleep (0.1)

2016/12/30_python