學習資料： https://github.com/hhatto/autopep8
背景
autopep8 會根據 PEP 8 樣式文件來格式化 python 程式碼。它使用 pep8 來決定程式碼的哪部分需要被格式化。 autopep8 可以修復 pep8彙報的大部分格式問題。
PEP8 是 Python Enhancement Proposal 的縮寫，翻譯過來就是 python 增強建議書， 是python的一個官方樣式指導。它規定了一些比較好的編碼方式，比如用4個空格代替縮排等等。
PEP 0008 -- Style Guide for Python Code： https://www.python.org/dev/peps/pep-0008/
安裝
$ pip install --upgrade autopep8
用法
usage: autopep8 [-h] [--version] [-v] [-d] [-i] [--global-config filename] [--ignore-local-config] [-r] [-j n] [-p n] [-a] [--experimental] [--exclude globs] [--list-fixes] [--ignore errors] [--select errors] [--max-line-length n] [--line-range line line] [files [files ...]] Automatically formats Python code to conform to the PEP 8 style guide. positional arguments: files files to format or '-' for standard in optional arguments: -h, --help show this help message and exit --version show program's version number and exit -v, --verbose print verbose messages; multiple -v result in more verbose messages -d, --diff print the diff for the fixed source -i, --in-place make changes to files in place --global-config filename path to a global pep8 config file; if this file does not exist then this is ignored (default: ~/.config/pep8) --ignore-local-config don't look for and apply local config files; if not passed, defaults are updated with any config files in the project's root directory -r, --recursive run recursively over directories; must be used with --in-place or --diff -j n, --jobs n number of parallel jobs; match CPU count if value is less than 1 -p n, --pep8-passes n maximum number of additional pep8 passes (default: infinite) -a, --aggressive enable non-whitespace changes; multiple -a result in more aggressive changes --experimental enable experimental fixes --exclude globs exclude file/directory names that match these comma- separated globs --list-fixes list codes for fixes; used by --ignore and --select --ignore errors do not fix these errors/warnings (default: E24) --select errors fix only these errors/warnings (e.g. E4,W) --max-line-length n set maximum allowed line length (default: 79) --line-range line line, --range line line only fix errors found within this inclusive range of line numbers (e.g. 1 99); line numbers are indexed at 1
特性
autopep8會修復pep8彙報的下列問題：
E101 - Reindent all lines. E121 - Fix indentation to be a multiple of four. E122 - Add absent indentation for hanging indentation. E123 - Align closing bracket to match opening bracket. E124 - Align closing bracket to match visual indentation. E125 - Indent to distinguish line from next logical line. E126 - Fix over-indented hanging indentation. E127 - Fix visual indentation. E128 - Fix visual indentation. E20 - Remove extraneous whitespace. E211 - Remove extraneous whitespace. E22 - Fix extraneous whitespace around keywords. E224 - Remove extraneous whitespace around operator. E226 - Fix missing whitespace around arithmetic operator. E227 - Fix missing whitespace around bitwise/shift operator. E228 - Fix missing whitespace around modulo operator. E231 - Add missing whitespace. E241 - Fix extraneous whitespace around keywords. E242 - Remove extraneous whitespace around operator. E251 - Remove whitespace around parameter '=' sign. E26 - Fix spacing after comment hash for inline comments. E265 - Fix spacing after comment hash for block comments. E27 - Fix extraneous whitespace around keywords. E301 - Add missing blank line. E302 - Add missing 2 blank lines. E303 - Remove extra blank lines. E304 - Remove blank line following function decorator. E309 - Add missing blank line (after class declaration). E401 - Put imports on separate lines. E501 - Try to make lines fit within --max-line-length characters. E502 - Remove extraneous escape of newline. E701 - Put colon-separated compound statement on separate lines. E70 - Put semicolon-separated compound statement on separate lines. E711 - Fix comparison with None. E712 - Fix comparison with boolean. E721 - Use "isinstance()" instead of comparing types directly. W291 - Remove trailing whitespace. W293 - Remove trailing whitespace on blank line. W391 - Remove trailing blank lines. W601 - Use "in" rather than "has_key()". W602 - Fix deprecated form of raising exception. W603 - Use "!=" instead of "<>" W604 - Use "repr()" instead of backticks. W690 - Fix various deprecated code (via lib2to3).
備註：
autopep8 也會忽略一些 pep8 的問題。
1. E112/E113
2. E265
autopep8 也會修復一個非pep8彙報的問題：
1. 糾正棄用的以及非慣用的python程式碼（通過 lib2to3）。這會讓python 2.6 以及 python 2.7 的程式碼更加與 python3 相容。（如果 W690 是enable的，這一項修復會被觸發）
2. 標準化具有多種行結束符的檔案。
3. 在類申明和它的第一個方法申明中間加一個空行。（由 E309 enable）
4. 在類文件和它的第一個方法申明中間加一個空行。（由 E301 enable）
5. 移除方法申明和它的文件之間的空行。 （由 E303 enable ）
具體用法
1. 使用 autopep8 更改一個檔案。
假設檔名是 a.py，檔案內容如下：
import math, sys; def example1(): ####This is a long comment. This should be wrapped to fit within 72 characters. some_tuple=( 1,2, 3,'a' ); some_variable={'long':'Long code lines should be wrapped within 79 characters.', 'other':[math.pi, 100,200,300,9876543210,'This is a long string that goes on'], 'more':{'inner':'This whole logical line should be wrapped.',some_tuple:[1, 20,300,40000,500000000,60000000000000000]}} return (some_tuple, some_variable) def example2(): return {'has_key() is deprecated':True}.has_key({'f':2}.has_key('')); class Example3( object ): def __init__ ( self, bar ): #Comments should have a space after the hash. if bar : bar+=1; bar=bar* bar ; return bar else: some_string = """ Indentation in multiline strings should not be touched. Only actual code should be reindented. """ return (sys.path, some_string)
轉到 Python3\Scripts 路徑，可以看到 autopep8.exe 檔案。
在a.py路徑下，開啟cmd，執行下列命令：
D:\Python3\Scripts\autopep8 --in-place --aggressive --aggressive a.py
備註：
--in-place： 以更改後的檔案直接替代原始檔。
--aggressive --aggressive : 以 aggressive 等級2 來更改原始檔。
更改之後，a.py內容如下：
import math import sys def example1(): # This is a long comment. This should be wrapped to fit within 72 # characters. some_tuple = (1, 2, 3, 'a') some_variable = { 'long': 'Long code lines should be wrapped within 79 characters.', 'other': [ math.pi, 100, 200, 300, 9876543210, 'This is a long string that goes on'], 'more': { 'inner': 'This whole logical line should be wrapped.', some_tuple: [ 1, 20, 300, 40000, 500000000, 60000000000000000]}} return (some_tuple, some_variable) def example2(): return ('' in {'f': 2}) in {'has_key() is deprecated': True} class Example3(object): def __init__(self, bar): # Comments should have a space after the hash. if bar: bar += 1 bar = bar * bar return bar else: some_string = """ Indentation in multiline strings should not be touched. Only actual code should be reindented. """ return (sys.path, some_string)
2. aggressive 等級
預設情況下，autopep8只修復空格問題。所以，預設情況下，autopep8不會修復 E711 和 E712 ，也不會修復棄用的程式碼 W6。
為了應用這些更加 aggressive 的修復，使用 --aggressive 選項：
autopep8 --aggressive a.py
使用多個 --aggressive 可以增加 aggressiveness 等級。
比如， E712 需要 aggressiveness 等級2.
autopep8 --aggressive --aggressive a.py
3. 選擇修復部分規範
只修復一部分規範，使用 --select 選項。
比如，修復多種縮排問題：
$ autopep8 --select=E1,W1 a.py
僅僅修復棄用程式碼問題：
$ autopep8 --aggressive --select=W6 a.py
4. 顯示詳細的過程資訊
$ autopep8 -v a.py
5. 以模組的方式使用
>>> import autopep8 >>> autopep8.fix_code('x= 123\n') 'x = 123\n'
6. 以模組的方式使用，且帶有條件
>>> import autopep8 >>> autopep8.fix_code('x.has_key(y)\n', options={'aggressive': 1}) 'y in x\n' >>> autopep8.fix_code('print( 123 )\n', options={'ignore': ['E']}) 'print( 123 )\n'