Python's third day study summary

1. Collection
The set mainly carries out the heavy and relational operations on the elements inside, and the permutation of elements is unordered.
A. Operation of the collection
############ #去重
Set1 = {1,1,2,2,3,4,4,5}
Print (Set1) #输出set1 = {1,2,3,4,5}
############# #增加值
Set1 = {1,1,2,2,3,4,4,5}
Set1.add (6)
Print (Set1) #输出set1 = {1,2,3,4,5,6}
Set1.update (' abc ')
Print (Set1) #输出set1 = {1,2,3,4,5,6, ' a ', ' B ', ' C '}
############## #删除
Set1.pop () #随机删除
Set1.remove (' A ') # is deleted according to the element, if no this element will error
Set1.clear () #清空集合
Del Set1 #删除集合
################ #查询
Query with for loop because the elements of the collection are unordered
B. Relational operations for sets
Set1 = {1,2,3,4,5} Set2 = {1,2,3,7,8}
Print (Set1 & Set2) #交集. Output {1, 2, 3}
Print (Set1 | set2) #并集. Output {1, 2, 3, 4, 5, 7, 8}
Print (Set1-set2) #差集. Output {4, 5}
Print (SET2-SET1) #差集. Output {7, 8}
Print (set1 ^ set2) #反交集. Output {4, 5, 7, 8}
Print (Set1 < Set2) #子集. Output false
Print (Set2 > Set1) #超集. Output false

2. Depth copy
##### #浅copy The first layer is independent, starting with the second layer, sharing a memory address
S1 = [1, 2, 3,[11,22]]
S2 = s1.copy ()
S1[-1].append (666)
Print (s1, S2) #s1和s2一样的值
Print (ID (s1), ID (S2)) #s1和s2的内存id不同
Print (ID (s1[-1]), ID (s2[-1])) #内层列表的id值是一样的
Deep copy no matter how many layers, are independent of each other
Import Copy
S1 = [1, 2, 3,[11,22]]
S2 = copy.deepcopy (S1)
S1.append (4)
Print (s1, S2) #只有s1增加了4, S2 does not increase by 4, indicating that the first layer is not the same memory address
S1[-1].append (#在内层的列表增加值33)
Print (s1, S2) #只有s1内层列表增加了33, S2 does not increase by 33, indicating that the inner layer is not the same memory address

3. File operation
Execution flow of file operations: Open file, generate file handle (F1)---manipulate file handle (open ())---Close file handle (F1.close ())
####### #文件的读
R mode:
F1 = open (' 123.txt ', encoding= ' UTF8 ', mode= ' R ') #123. txt to present the current directory, or it will error
Print (F1.read ()) #打印读取的内容
F1.close () #关闭文件句柄
F1.read (n) #按照字符读取, n represents n characters
F1.readline () #按行读取
F1.readlines () #返回列表 that contains all the rows
RB mode (read non-literal Class):
F1 = open (' 1.jpg ', mode= ' RB ') #1. jpg to present the current directory, or it will be an error
Print (F1.read ())
F1.close ()
F1.read (n) #按照字节读取, n represents n bytes
For loop mode: One cycle consumes a piece of memory and is released after the loop.
r+ mode and R+b mode are similar to the above modes.
############# #文件的写
F1 = open (' 456.txt ', encoding= ' utf-8 ', mode= ' W ') #没有文件, create a new file to write to, have the original file, empty the content, and then write the new content
Print (F1.write (' 456 '))
F1.close ()
WB mode (write to non-literal class)
F2 = open (' 2.jpg ', mode= ' WB ')
F2.write (F1.read ()) #f1. Read () reads a picture content
F2.close ()
w+ mode and W+b mode are similar to the above modes.
############## #文件的追加
F1 = open (' 456.txt ', encoding= ' utf-8 ', mode= ' a ') #没有文件, new file write content, original file, add on base of source file
Print (F1.write (' 789 '))
F1.close ()
AB Mode A + mode a+b mode is similar to the above mode
######## #文件的其它常用操作
F1.seek () #调整光标的位置
F1.tell () # Tell the cursor where
With open (' 123.txt ', encoding= ' utf-8 ') as F1 #不用主动关闭文件句柄

4. Primary knowledge function
Function: function-oriented to solve the problem of multiple readability of repeated code
Definition of the function:
def keyword function name ():
function body
Function execution: function name ()
Return of the function: terminates the function or returns a value to the performer of the function.
Parameters of the function:
######## #实参角度
A. Position parameters correspond to order one by one
Def func1 (A, B, c):
Print (A, B, c)
Func1 (1, 2, 3) #a =1 b=2 c=3
B. keyword parameter one by one correspondence
Def func1 (A, B, c):
Print (A, B, c)
Func1 (C=1,b=2,a=3)
C. Mixed parameters (including positional and keyword parameters), the keyword parameter must be behind the position parameter
Def func1 (A, B, c):
Print (A, B, c)
Func1 (1,2,c=3)
########### #形参角度
A. Position parameters correspond to order one by one
Def func1 (A, B, c):
Print (A, B, c)
Func1 (1, 2, 3) #a =1 b=2 c=3
B. Default parameter, the default parameter is after the position parameter.
Def func1 (A, B, c=3):
Print (A, B, c)
Func1 (ON)
############ #动态参数 args: All positional parameters are placed in a tuple. Kwargs: All the keyword parameters, put in a dictionary
def func1 (*args, Kwargs): #函数的定义的时候represents aggregation
Print (args)
Print (Kwargs)
Func1 ([1, 2, 3],{' name ': ' CC ', ' Age ': '} ') #函数的执行的时候representative
Order of formal parameters: Positional parameter--args--default parameter--**kwargs

Python's third day study summary