Fifth day of basic Python learning

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5.1-depth Copy

5.1.1 Shallow Copy

5.1.2 Deep Copy

5.2 Collection Set

5.2.1 Update Set Collection _ Add

5.2.2 Update

5.2.3 Remove, Pop, clear, Del

5.2.4 intersection, and set

5.2.5 difference Set, symmetric difference set

5.2.6 Hyper-Set, subset

5.3 Functions:

5.3.1, Concept

5.3.2, creating

5.3.3, Parameters

The reture of 5.3.4 and functions

5.3.5, defining domains

# symbol Description

() #元组 Usage: (' xx ', ' yy ') not modifiable

[] #列表 usage: [' xx ', ' yy '] can be modified, the list must be hash, list and dictionary is not hash

List creation: a=[1,2]

B=list ([up])

{} #字典 Usage: {' xx ': ' yy ', (' zz ': ' DD ')} modifiable fields

5.1-depth Copy

5.1.1 Shallow copy = equivalent to soft link

# Variables in the list is equivalent to a file, int and STR is equivalent to a directory,

# (Soft links can name the directory more than the file itself, but if you modify the file then A and B will be modified at the same time).

A = [[1,2],3,4]

Print (a)

Printed: [[1, 2], 3, 4]

b = A.copy ()

b[1]=321

Print (b)

The result is: [[1, 2], 321, 4]# Soft Link directory name changed and will not affect the original directory

Print (a)

The results are as follows: [[1, 2], 3,4] # B Modifying a without modification is normal.

# But if you modify the list in a variable, it modifies the value in the memory, and a and B modify the

B[0][1] = 234

Print (b)

Print (ID (b[0][1))# The result is: 13,889,648,802 memory results are the same

Print (a)

The printed result is: [[1, 234], 321, 4] # changed the soft link file, then 2 files will also be called

[[1, 234], 3, 4]

Print (ID (a[0][1))) # The result is: 1388964880

# equivalent to a linked file, modify B is also equivalent to modifying a

5.1.2 Deep copy = Full clone

Variable = copy.deepcopy (variable to copy) # Complete cloning of one data

5.2 Set

Set: A set of different elements formed together, is the basic data type of the PY

# Redo function, when there are two identical elements will remove the duplicate string

# must be a hash string, set is unordered and can only be accessed or judged by looping through or using in and not

# Set cannot be a key

5.2.1 Update Set Collection _ Add

A = ["A", "B"]

C=set (a)

C.add ("C")

Print (c) result: {' B ', ' A ', ' C '}

5.2.2 Update

C.update ("AB1")

Print (c) result: {' B ', ' 1 ', ' A ', ' C '}

# AB1 is added as a sequence, there are duplicates not added to the sequence, no duplicates are added directly to the list

C.update ([123,321]) # when it is a list, it joins the sequence as a whole into the variable, with duplicates and does not add

Print (c)# {321, ' B ', ' A ', 123}

5.2.3 Remove, Pop, clear, Del

C.remove ("a") result: {' B ', ' 1 ', ' C '}

C.pop () result: randomly deletes a

C.clear ()# Result: Empty list return set ()

del c # directly delete the variable, print the error because it's gone.

5.2.4 intersection, and set

A=set ([1,2,3,4,5])

B=set ([1,2,3,4,6])

Intersection: Print (A & B) # {1, 2, 3, 4}

Assembly: Print (A | b) # {1, 2, 3, 4, 5, 6}

5.2.5 difference Set, symmetric difference set

Difference set: Print (A.difference (b)) in a but bot B # a There's no printout of B

Second method: Print (A-B)

# {5} and vice versa

Symmetric differential set: print (A.symmetric_difference (b)) AB does not print, only print a string or numeric value that it does not share

Second method: Print (A^B)

# {5, 6}

5.2.6 Hyper-Set, subset

Print (A.issuperset (b))# A is not completely inclusive B, no return False equals a>b

Print (A.issubset (b))# A is not a subset of B equals a<b

Name1=set (["Xiong", "Wei", "Hua", "FA"])

Name2=set (["Xiong", "Yua", "Yuan", "Hua"])

# subset # To determine if two fields are equal

Print (name1<name2) # False

# Parent Set # Determines whether two fields are equal

Print (name1>name2) # False

# and set # after printing to go back to the

Print (name1 | name2) # {' Hua ', ' Xiong ', ' yuan ', ' Wei ', ' fa ', ' Yua '}

# intersection # Common

Print (Name1 & name2) # {' Hua ', ' Xiong '}

# difference # Subtract the same field from set 2 with Set 1, and take out a collection that is not related to 2

Print (name1-name2) # {' Wei ', ' FA '}

# symmetric difference Set # take out A and b Yes, print a string that doesn't have two sets

Print (name1 ^ name2) # {' Yuan ', ' yua ', ' fa ', ' Wei '}

# Manually enter some strings to compare with a self-defined string

Ins=[]b=set ([' 1 ', ' 2 ', ' 3 ', ' 4 ', ' 5 ']) while True:a=input ("test:") if a = = "Q": Break Ins.append (a) ins=set (INS) Print (Ins > B)

5.3 Functions:

5.3.1, Concept

Role:

1. Reduce duplication of code

2, easy to modify, easy to expand

3. Maintain Code consistency

Naming rules

The function name must begin with an underscore or a letter, can contain any combination of letters, numbers, or underscores, and cannot use any punctuation

Function names are case-insensitive;

The function name cannot be a reserved word.

5.3.2, creating

def f (): # DEF is a define abbreviation F () means the function name () can be used to pass parameters

Print ("Hello World") # function body, all the code below belongs to the F function

F ()# Call function, without (), directly with F then it is represented as a variable

5.3.3, Parameters

# Note: 1, the number of parameters, the argument must be defined how many

2, the call should be strictly case-sensitive

3, the dictation parameters must be followed by other parameters

4, indefinite long parameters, fixed format: (*args No named parameters left, **kwargs have named parameters put to the right), if there are default parameters left

# must parameter (keyword argument): The parameter must be passed into the function in the correct order, and the number of calls must be the same as when declared

def add (x, y): # Add (x, y) parameter

Print (X+y)

def (3,5)# arguments

def test1 (name,age):

Print ("Name:%s"% name)

Print ("Age:%d"% of age)

Test1 ("Xiong", 123)

Print Result: Name:xiong

Age:123

# Default Parameters:

def test1 (name,age,sex= "man"):

Print ("Name:%s"% name)

Print ("Age:%d"% of age)

Print ("Sex:%s"% sex)

Test1 ("Xiong", 123)

Print Result: Name:xiong

Age:123

Sex:man

# Indefinite length parameter: (*args) # args can name * indicates indefinite length parameter

(*arges): No named parameter # is a tuple when saved to args

(**kwargs): Dictionary with named parameter # saved to Kwargs

def test2 (*args): print (args) test2 (1,2,3,4,5,6) # The results are: (1, 2, 3, 4, 5, 6)

##################### Example 2 #####################

def test3 (**kwargs): Print (Kwargs) test3 (name= "Xiong", age=123,sex= "man") # Print Result: {' name ': ' Xiong ', ' age ': 123, ' sex ': ' m An '}

##################### Example 3 #####################

def test3 (**kwargs): For Te in Kwargs:print (Te, ":", Kwargs[te]) test3 (name= "Xiong", age=123,sex= "man") # Print Results: Name:xiong age:123 Sex:man

##################### Example 4 #####################

def test4 (*args,**kwargs): Print (Args,kwargs) test4 (1,2,3,4,name= "Xiong", age=123,sex= "man") # Print Result: (1, 2, 3, 4) {' Name ' : ' Xiong ', ' age ': 123, ' sex ': ' Man '}

##################### Error--Example 5 #####################

def test4 (name,sex= "man", *args,**kwargs): Print (Name,sex,args,kwargs) test4 (name= "Xiong", sex= "man", 1,2,3,4,age= 123) # Print Result: syntaxerror:positional argument follows keyword argument

# Priority: Def function name (key parameter, default parameter, no named parameter, named parameter)

#示例 def test (te1,age= ' male ', 123,job= ' IT ')

######### when there is a default value in the middle, if you do not specify it or will print an error,

def test4 (name,sex= "man", *args,**kwargs): Print (Name,sex,args,kwargs) test4 ("Xiong", 1,2,3,4,age=123)

The reture of 5.3.4 and functions

Effect: 1, End Function

2. Return an Object

Note: 1. If there is no return in the function, it will return a none by default

2, if return has more than one object, then Python will help us encapsulate multiple objects into a tuple to return

5.3.5, defining domains

The function has its own domain, if it is not.

The scope is divided into four kinds of situations: LEGB

l:local, local scope, which is the variable defined in the function;

E:enclosing, the local scope of the nested parent function, which is the local scope of the ancestor function that contains the function, but not the global;

G:globa, a global variable, is a variable defined at the module level;

B:built-in, the variables inside the system fixed module, such as int, ByteArray, etc. The order of precedence for a search variable is: scope local > Outer scope > Global >python Built-in scope in the current module, that is, LEGB

Outer built-in--global scope--enclosing local scope--local area scope

Local variables cannot modify global variables

Local to change global variables need to add one global variable

If it's in enclosing, then you need to add a nonlocal variable name

Module: Remove Current time

Import time

Time_format = '%y-%m-%d%x '

Times = Time.strftime (Time_format)

Print (Times)

# function, set a function time, save it to the test file, will print start funcation to the screen

#!/usr/bin/env python#-*-coding:utf-8-*-def Logger (n): Import time Time_format = "%y-%m-%d%x" times = Time.st Rftime (Time_format) with open ("Test file", ' a ', encoding= ' Utf-8 ') as F:f.write ("%s Funcation1%s \ n"% (times,n)) def F                      UN1 (n): Print ("Start funcation 1") Logger (n) fun1 (1) # Print results open test file 2017-09-12 14:13:33 funcation1 1 #%s times Parameters for the%s n function parameter

# Implement the addition of indefinite long functions

def test2 (*args): number = 0 for i in Args:number + = i print (number) test2 (1,2,3,4,5,6) # Pass a bunch of integers to the test2 function, protect Save to Args is a tuple format with a For loop overlay

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Fifth day of basic Python learning