[zero basics of Python to introduction] a prerequisite for Python preparatory knowledge -- basic coding specification of Python

Preface

• This article is 【Python Zero foundation to introductory column 】 Learn a series of articles
• Python special column Portal Here it is ：https://blog.csdn.net/zhangay1998/category_11086734.html
• In this article, let's talk about Python Basic coding specification , It's also Python A necessary operation on the road ~
• Tips ： The environment configuration of this article is Python3 Development environment of , Follow up tutorials are also Python3

Python Coding standards

Coding standards It exists in all kinds of programming languages , Maybe some languages are not very intuitive

If you are a novice, learn to write code , So from the beginning Memorize coding rules It will have a great impact on the future compilation of specifications ！

Here is a brief introduction to several coding specifications that beginners should keep in mind , It is divided into several aspects to introduce , Let's have a look ！

Python use PEP 8 As coding specification , among PEP yes Python Enhancement Proposal（Python Enhancement proposal ） Abbreviation ,8 It stands for Python Code style guide .

Let's take a look at the code in a picture

Compare with the picture above Two pieces of code in can find , They contain exactly the same code

But the coding format on the right obviously looks more regular than the code snippet on the left , It will also be easier to read 、 Carefree , Because it follows the most basic Python Code specification .

The following is divided into several parts to learn Python Code specification of , Make our code more beautiful 、 beautiful ！

️‍ Declaration encoding format

• Generally speaking , The declaration encoding format is required in the script

• If python The source code file There is no declared encoding format ,python The interpreter will default to ASCII code

• But one disadvantage of this is , In case of non ASCII Encoded character ,python The interpreter will report an error

• With UTF-8 For example , The following two kinds of encoding format statements are in line with the rules .

# -*- coding: utf-8 -*-

# coding = utf-8

️‍ Indent rules

• And other programming languages （ Such as Java、C Language ） Use braces “{}” Separate code blocks are different ,Python Using code indents and colons （ : ） To distinguish the layers between blocks of code .

• stay Python in , For class definitions 、 Function definition 、 Flow control statement 、 Exception handling statements, etc , The colon at the end of the line and the indent of the next line , Indicates the beginning of the next block of code , The end of the indentation indicates the end of the code block .

• Be careful ,Python Indent the code in , You can use spaces or Tab Key implementation . But whether it's manual typing spaces , Or use Tab key , Usually use 4 Space length as an indent （ By default , One Tab The key means 4 A space ）.

• about Python Indent rules , Beginners can understand ,Python Require lines of code that belong to the same scope , They must be indented by the same amount , But the exact amount of indentation , No hard and fast rules .

Correct sample code ：

a=1
if a==1:
print(" correct ") # Indent 4 Empty space 
else: # And if alignment 
print(" error ") # Indent 4 Empty space 

Error example code ：

a=1
if a==1:
print(" correct ")
else:
print(" error ")
print("end") # To correct, just delete the space in front of this line of code 

Just remember a little ： Unified use 4 Space to indent , Do not use tab, No more tab Mixed with Spaces

Remember that , Generally speaking, indentation will not cause too much problem ！

️‍ Comment part

Python Use in # Annotate , We are using # When ,# There should be a space behind the number

 # Comment part 
# 
# Comment part 

When commenting in the line , At least two spaces should be added in the middle

print(" Hello , The world ") # notes 

️‍ Space

Space General principles used ：

• One space on each side of a binary operator , The spaces on both sides of arithmetic operators can be used flexibly , But make sure both sides are consistent
• Don't use commas 、 A semicolon 、 A colon is preceded by a space , But they should be followed by （ Except at the end of the line ）
• Function's argument list , There should be a space after the comma
• Function's argument list , The default value is equal sign without spaces
• After the left bracket , Don't add space before the right parenthesis
• parameter list , There should be no space in front of the left bracket of the index or slice

Usually , On both sides of the operator 、 Between function arguments and both sides of commas , It is recommended to use spaces to separate .

️‍ Blank line use

Blank line General principles used ：

• Code format statement 、 Module import 、 Constant and global variable declarations 、 There are two lines between the top-level definition and the execution code
• There are two empty lines between the top-level definitions , Empty a line between method definitions
• Inside a function or method , You can empty a line where necessary to enhance the sense of rhythm , But we should avoid continuous empty lines

Using the necessary blank lines can increase the readability of the code , Usually defined at the top level （ Such as the definition of a function or class ） There are two lines in between , There is a blank line between the method definitions , In addition, a line can be left blank in the position used to separate certain functions .

️‍ Module import part

The import should always be at the top of the file , After module comments and document strings , Before module global variables and constants .

Imports should be grouped from the most common to the least common , Leave a line blank between groups ：

• Standard library import
• Third party library import
• The application specifies the import

Every import Statement imports only one module , Try to avoid importing multiple modules at once

# recommend 
import os
import sys
# Not recommended 
import os,sys

️‍ Naming specification

Everyone should be familiar with the naming convention , But the explicit specifications of different programming languages are also different ~

Python General principles for naming recommendations ：

• Modules should be named in lowercase as much as possible , Keep the initials in lowercase , Try not to underline
• Class names use humps (CamelCase) Naming style , title case , Private classes can start with an underscore
• All function names are lowercase , If there are more than one word , Separate... With underscores
• Private functions can start with an underline
• Try to lower the variable name , If there are more than one word , Separate... With underscores
• Constants are in uppercase , If there are more than one word , Use an underline to separate

️‍ Quotation mark usage

Python in , Single and double quotation marks can be used correctly in the output statement , But there are also corresponding coding specifications

So let's not add quotation marks at will , It is best to follow the following specifications ！

General principles for the use of quotation marks ：

• Natural language uses double quotation marks
• The machine identification uses single quotation marks
• Regular expressions use double quotes
• docstring (docstring) Use three double quotes

️‍ Semicolon usage

Python It is very different from the semicolon used in several other mainstream programming languages
Python You don't need a semicolon at the end of your code , and Java and C# And so on

Don't add a semicolon to the end of a line , And don't use semicolons to put two commands on the same line , for example ：

# Not recommended 
print("Hello") ; print("World")

summary

About beginners Python The basic coding specification probably needs special attention ！

We followed the coding rules from the beginning , Develop a good coding habit , It is also a good start for learning programming ！