Python Knowledge Review

Read Catalogue

• A data type
• Two anonymous functions
• Three adorners, generators, iterators
• Four sort, sorted
• Five-list derivation, generator expression,
• Six and-or
• Seven map functions
• Eight multi-threaded multi-process Gil
• Nine OS, sys module
• Ten static methods, class methods, instance methods
• 11 Memory Management
• 12 *args **kwargs
• Thirteen-One Some database operations
• 14 default list parameter memory address l=[]
• The difference between IS and = =, in
• 16 single-Case mode

One data type 1 numbers

Integral type and floating point type

# int# Essence Age=int (#)# float float# Essence salary=float (3000.3)# binary, decimal, octal, hex 

Other number types (understanding)

# Long Plastic (understanding)     in Python2 (no long shaping concept in Python3):    >>> num=2l    >>> type (num)    'long' ># plural (learn) >>> x=1-2j >>> x.real 1.0 >>> X.imag- 2.0         

2 string

# function: Name, gender, nationality, address, etc. description information # definition: in single quotation marks \ double quotes \ Three quotation marks, consisting of a string of characters name='Egon'# precedence operation: value by index (positive fetch + reverse fetch): only slices (Gu Tou regardless of tail, stride length) Len member operation in and not in
Remove blank strip split splits
Cycle

3 List

#Role: Multiple equipment, multiple hobbies, multiple courses, multiple girlfriends, etc.# definition: [] can have multiple values of any type, comma separated my_girl_friends=['Alex ','Wupeiqi',' Yuanhao ', 4,5] # Nature my_girl_friends=list ([...]) or L=list ('ABC')# Priority operation: Indexed access value (forward Access + reverse access): can be saved or sliced (Gu Tou regardless of tail, step) Length member operations in and not in
Append Delete loop                   

#PS: Reverse step l=[1,2,3,4,5,6]##[1, 2, 3]##[3, 2, 1] # #[6, 5, 4, 3, 2, 1] 

　

4 tuples

# function: To store multiple values, in contrast to the list, the tuple is immutable (which can be used as a dictionary key), mainly to read the # definition: Compared to the list type, but [] replaced by () age= (11,22,33,44,55) Nature Age=tuple (( 11,22,33,44,55)# Priority operations: Value by index (positive fetch + reverse fetch): only slices (Gu Tou regardless of tail, step) length member operation in and not in loop    

　

5 Dictionaries

#Function: Store multiple values, Key-value access, fast value#Definition: Key must be an immutable type, value can be any type info={‘Name‘:‘Egon‘,‘Age': 18,‘Sex‘:‘Male‘}#Essential Info=dict ({...})or Info=dict (name=‘Egon', age=18,sex=‘Male‘) or info=dict ([[ "name", " egon "age", 18 ' name",  ' age ",  "sex"  ), None) # precedence operation:  Access value by key: The available length Len member operation in and not in Delete key (), value values (), key value pair items () loop        

　

#Resolving duplicate assignments with SetDefault‘‘‘SetDefault function 1:key exist, then do not assign a value, key does not exist, set the default value 2:key exist, return the key corresponding to the existing value, key does not exist, return is to set the default value D={}print (D.setdefault (' A ', 1)) #返回1d ={' a ': 2222}print (D.setdefault (' A ', 1)) #返回2222‘‘‘s=‘Hello Alex Alex say hello SB sb‘Dic={}words=S.split ()for word in words: #word= ' Alex '  Dic.setdefault (Word,s.count (word)) print (DIC) #  Take advantage of the set, remove the repetition, reduce the number of cycles S= '  Hello Alex Alex say hello sb sb ' dic={}words=s.split () Words_set=set (words) for word in words_set:dic[word]=< Span style= "COLOR: #000000" >s.count (word) print (DIC)      

 6 Collection   

 # function: de-weight, relational operation, # definition:  knowledge point review mutable types are non-hash type immutable types are hash types # definition collection:  collection: can contain multiple elements, separated by commas , the elements of the collection follow three principles: 1: Each element must be an immutable type (hash, can be a key to the dictionary) 2: No duplicate elements 3: unordered note the purpose of a collection is to store different values together, and to do relational operations between different sets, without having to tangle with individual values in the collection # precedence operation:  Length Len member operation in and not in| Collection & intersection- symmetric difference ==> , >=, <,<= parent set, subset             

7 Summary of data types

Sub-footprint (low to high) per storage space

Numeric string collection: unordered, that is, unordered storage index related information tuple: ordered, need to store index related information, immutable list: Orderly, need to store index related information, variable, need to deal with the data to change the dictionary: unordered, need to save key and value mapping information, variable, need to deal with data deletion and modification

Differentiate by number of stored values

Scalar/Atomic Type	Number, string
Container type	list, tuple, dictionary

By Variable immutable distinction

Variable	List, dictionary
Not variable	Numbers, strings, tuples

Differentiate by Access order

Direct access	Digital
Sequential access (sequence type)	String, list, tuple
Key value access (mapping type)	Dictionary

A functional Knowledge system

1 What is a function? 2 Why use a function? 3 Classification of functions: Built-in functions and custom functions 4 How to customize function  syntax  define parametric functions, and application scenarios with parametric functions to  define parameterless functions, and application scenarios for parameterless functions  to define empty functions, and application scenarios for empty functions 5 Call function    How to call function    function    parameter application: Formal parameter and argument, positional parameter, keyword parameter, default parameter, *args,**KWARGS6 higher order function (function object) 7  Function nesting 8 scope and namespace 9 adorner and generator and co-op function one-by-one ternary operation, list parsing, generator expression, recursive invocation of the function of the three functions 14 for process programming and functional programming 

The basis of two functions

Links: http://www.cnblogs.com/linhaifeng/articles/7531972.html

Three function objects, function nesting, namespaces and scopes, adorners

Links: http://www.cnblogs.com/linhaifeng/articles/7532497.html

Four iterators, generators, process-oriented programming

Links: http://www.cnblogs.com/linhaifeng/articles/7580428.html

53-Tuple expressions, list derivations, generator expressions, recursion, anonymous functions, built-in functions

Links: http://www.cnblogs.com/linhaifeng/articles/7580830.html

Six function drafts

This is the draft part of the above content, the reader does not need to see

Draft: http://www.cnblogs.com/linhaifeng/articles/6883726.html

Seven jobs

Job Requirements:

Analog implementation of an ATM + shopping mall Program

1. Quota 15000 or Custom
2. Realize shopping mall, buy things to add shopping cart, call credit card interface Checkout
3. Can withdraw, handling fee 5%
4. 22nd monthly Billing, 10th monthly repayment date, overdue, according to the total amount owed 5 daily interest
5. Multi-Account Login support
6. Support transfer between accounts
7. Record monthly daily consumption flow
8. Provide repayment interface
9. ATM Record Operation Log
10. Provide management interface, including adding account, user quota, freezing account, etc...
11. Decorator for user authentication

Sample Code HTTPS://GITHUB.COM/TRIAQUAE/PY3_TRAINING/TREE/MASTER/ATM

Simple flowchart: https://www.processon.com/view/link/589eb841e4b0999184934329

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Python Knowledge Review