What is? Python？
- Dynamic interpretive language ,1982 Year by the Dutch Guido von Rossum The invention .
- More details can be google, There is no expansion here .
Python Interpreter ：
- CPython（ Official version C Language implementation ）
- IronPython（ Can run in .NET and Mono platform ）
- PyPy（Python Realization , Support JIT Just in time compilation ）
- Jython（ Running on the Java platform ）
- This article is only for learning Cpython be based on Python3.8+
Python Advantages and disadvantages ：
- Simple , studies of the Book of Changes , Open source , object-oriented , Scalable , Rich wheels .
- Slow execution , Common faults of dynamic scripting languages , So computing intensive should rely on C Language and other compiler language implementation .
Python Philosophy of design
- clear ：
- In a way , It's better to have only one way to do one thing
- If there are multiple options ,Python Developers generally reject fancy Syntax , Choose a clear grammar that doesn't differ .
- Simple ： The code is as easy to understand as pure English .
- characteristic ： All things are objects .
- stay Python Interactive terminal input import this You can see Python zen
Python Application scenarios of
- Web application development ：Django,Flask,Tornado
- Operating system management , Server operation and maintenance , Automation script
- Web crawler ：Scrapy
- Scientific Computing ：NumPy,SciPy,Pandas,Matplotlib
- Desktop software （ Not very mature ）：PyQt,PySide,wxPython,PyGTK
- Server software ,APP There are also corresponding libraries , It's just that it may not be mature enough and the maintenance is not fast enough .
download Cpython Interpreter
- visit Python Official website ：https://www.python.org/
- Click on download Button , Select the system type in the drop-down box ( windows/Mac OS/Linux etc. )
- Select Download Python3 Version of , Suggest a new stable version
- Double click download okay Python package
- Check Add Python 3.8 to PATH then Install now
- Mac and Linux Sure google Installation method , And environment variable configuration .
Test for successful installation
- open Termal/cmd( The command line ） Input python, If the version number is displayed, the installation is successful ,
If appear ‘python’ Not an internal or external command , Nor are they runnable programs or batch files .
Manual configuration is required PATH, take python.exe Installation address of
Add to environment variables PATH in
Package manager pip Use
- pip It's a modern , General purpose Python Package management tools , Provide right Python Bag
lookup , download , install , Uninstall function , Convenient for Python Management of resource packages .
- install ： In the installation Python when , Will automatically download and install pip
pip To configure
- In the command line , Input pip -V You can see pip Version of .
- If appear ‘pip’ Not an internal or external command , Nor are they runnable programs or batch files , We need to be the same
C:\\Users\Eric\AppData\Local\Programs\Python\Python38\Scripts（pip.exe Address ） Add to user PATH In the environment variables .
Use pip management Python package
pip install <package_name>Install the specified package , for example ： pip install jango
pip uninstall <package_name>Delete / Uninstall the specified package
pip listDisplays a list of installed packages
pip freezeAnd list equally , Just for package==version Format lists
Packaging and importing environment ：
pip freeze > requirements.txtTalking about the current environment, all modules are packaged into requirements.txt In file
pip install -r requirements.txtinstall requirements.txt The packages listed in the file
Modify download source
- pip install <package_name> -i as follows
pip install flask -i https://pypi.douban.com/simple/Download and install from Douban source flask modular
（ Just temporarily use this Douban source , If not next time -i It's also the default source ）
- Permanent modification pip Download address ：
Create directories and configuration files C:\Users\Eric\pip\pip.ini And edit the following configuration information to save ：
Images are commonly used in China ：
- Alibaba cloud https://mirrors.aliyun.com/pypi/simple/
- University of science and technology of China https://pypi.mirrors.ustc.edu.cn/simple/
- douban https://pypi.douban.com/simple/
- Tsinghua University https://pypi.tuna.tsinghua.edu.cn/simple/
- University of science and technology of China https://pypi.mirrors.ustc.edu.cn/simple/
In fact, there is no need to change , A ladder is built by a wall [ funny ]
There are a lot of code editing tools , Yes vim、sublime、notepad++、VS code、Pychram etc.
The last two are recommended as integrated development environments
- Run on command line py file ：
- Install the professional version directly , Respect copyright and pay （ No more Chinese characteristics or some treasure ）
- Pychram Some of the tips ：
- Skillfully use . Number , such as a + b.print The carriage return will become print(a+b)
- ctrl+shift+k formatting code
- ctrl+ Left click the built-in function or module to quickly locate and view python Source code
Interactive programming ：ipython
notes -- Help developers read code , A statement that a program will not execute
# This is a single line comment pychram Shortcut key ctrl+/
''' So that's one Multiline comment Three single quotation marks for multiline comments '''
Definition of variables
- For data that is reused and often modified , Can be defined as variables to improve programming efficiency .
The syntax for defining variables
- Variable name = A variable's value （ there = The function is to assign a value, not equal to ）
for example key = value = True = 1
a , b = 1 , 3
a , b = b , a # Exchange assignments
a , *b = 1,2,3,4,5 # a=1 b = [2,3,4,5]
python Very flexible , Very clever .
Variable name specification
- Cannot use keyword （ Built in keywords into print,if etc. ）
- You can't start with a number
- I want to know the meaning of the name , Underline is recommended
- follow PEP8 standard ： Variable name , Function names and file names are all lowercase , Use underscores to connect ,
The class name follows the nomenclature of the great hump ; Constant names are all uppercase .
The right example ：student_name,user_name,user_id...
- Some identifiers with special functions , Has been python Official use , Developers are not allowed to define the same identifier as keywords themselves .
- See all the keywords ：
['False', 'None', 'True', 'peg_parser', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']
None of the above can be named as a new identifier .
- int plastic
- long Long integer [ It can also represent octal and hexadecimal ],python3 To be used as waste long
- float floating-point
- complex The plural
- True Boolean type bool, really
- False Boolean type , false
- str character string
- list list
- tuple Tuples
- dict Dictionaries
- set aggregate
View data type
a = "123"
print(type(a)) # type(） Return data type
<class 'str'> # This is a string
- The type does not need to be declared by the developer , Define variables and ,python It's smart enough to help us define types
- Output / Print ： Show the object results
unfinished , Continue in the afternoon ...
【 In seven days Python】day01.Python Environment configuration 、pip、IDE、 notes 、 Variable , data type 、 identifier / keyword 、 Output 、 Enter more related articles
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