之前一直用 Python IDLE 写代码，最近换成 PyCharm 写代码总是会出现波浪号，这才了解到 Python 的 PEP8 代码规范，所以将常见的 PEP8 代码规范问题和解决方法记录一下，学习一下，遇到了再持续更新，养成良好的习惯，编写规范的代码！
PEP的全称是Python Enhancement Proposals，其中Enhancement是增强改进的意思，Proposals则可译为提案或建议书，所以合起来，比较常见的翻译是Python增强提案或Python改进建议书。
PEP 8: no newline at end of file
解决方法：代码末尾需要另起一行，光标移到最后回车即可PEP 8: indentation is not a multiple of four
解决方法：缩进不是4的倍数，检查缩进PEP 8: over-indented
解决方法：过度缩进，检查缩进PEP 8: missing whitespace after’,’
解决方法：逗号后面少了空格，添加空格即可，类似还有分号或者冒号后面少了空格PEP 8: multiple imports on one line
解决方法：不要在一句 import 中引用多个库，举例：import socket, urllib.error最好写成：import socket import urllib.errorPEP 8: blank line at end of line
解决方法：代码末尾行多了空格，删除空格即可PEP 8: at least two spaces before inline comment
解决方法：代码与注释之间至少要有两个空格PEP 8: block comment should start with ‘#’
解决方法：注释要以#加一个空格开始PEP 8: inline comment should start with ‘#’
解决方法：注释要以#加一个空格开始PEP 8: module level import not at top of file
解决方法：import不在文件的最上面，可能之前还有其它代码PEP 8: expected 2 blank lines，found 0
解决方法：需要两条空白行，添加两个空白行即可PEP 8: function name should be lowercase
解决方法：函数名改成小写即可PEP 8: missing whitespace around operator
解决方法：操作符（’=’、’>’、’<'等）前后缺少空格，加上即可PEP 8: unexpected spaces around keyword / parameter equals
解决方法：关键字/参数等号周围出现意外空格，去掉空格即可PEP 8: multiple statements on one line (colon)
解决方法：多行语句写到一行了，比如：if x == 2: print('OK')要分成两行写PEP 8: line too long (82 > 79 characters)
解决方法：超过了每行的最大长度限制79PEP 8: Simplify chained comparison
可简化连锁比较（例如：if a >= 0 and a <= 9: 可以简写为：if 0 <= a <= 9:）
如果想要选择性忽略PEP8代码风格的警告信息可以使用以下方法：（养成良好的习惯，编写规范的代码！不推荐忽略！）
①将鼠标移到出现警告信息的地方，按 alt+Enter，选择忽略（Ignore）这个错误即可：
②依次选择 File - Settings - Editor - Inspections，在 Python下找到 PEP8 coding style violation 选项，在右下角的 Ignore errors 里点击加号可以添加需要忽略的警告信息ID（ID信息见后面附录），例如想要忽略indentation contains mixed spaces and tabs这个警告，只需要添加其ID：E101 即可
附录：全部警告信息以及对应的ID，官方地址：https://pep8.readthedocs.io/en/latest/intro.html#error-codes
code | sample message |
E1 | Indentation |
E101 | indentation contains mixed spaces and tabs |
E111 | indentation is not a multiple of four |
E112 | expected an indented block |
E113 | unexpected indentation |
E114 | indentation is not a multiple of four (comment) |
E115 | expected an indented block (comment) |
E116 | unexpected indentation (comment) |
E117 | over-indented |
E121 (*^) | continuation line under-indented for hanging indent |
E122 (^) | continuation line missing indentation or outdented |
E123 (*) | closing bracket does not match indentation of opening bracket’s line |
E124 (^) | closing bracket does not match visual indentation |
E125 (^) | continuation line with same indent as next logical line |
E126 (*^) | continuation line over-indented for hanging indent |
E127 (^) | continuation line over-indented for visual indent |
E128 (^) | continuation line under-indented for visual indent |
E129 (^) | visually indented line with same indent as next logical line |
E131 (^) | continuation line unaligned for hanging indent |
E133 (*) | closing bracket is missing indentation |
E2 | Whitespace |
E201 | whitespace after ‘(‘ |
E202 | whitespace before ‘)’ |
E203 | whitespace before ‘:’ |
E211 | whitespace before ‘(‘ |
E221 | multiple spaces before operator |
E222 | multiple spaces after operator |
E223 | tab before operator |
E224 | tab after operator |
E225 | missing whitespace around operator |
E226 (*) | missing whitespace around arithmetic operator |
E227 | missing whitespace around bitwise or shift operator |
E228 | missing whitespace around modulo operator |
E231 | missing whitespace after ‘,’, ‘;’, or ‘:’ |
E241 (*) | multiple spaces after ‘,’ |
E242 (*) | tab after ‘,’ |
E251 | unexpected spaces around keyword / parameter equals |
E261 | at least two spaces before inline comment |
E262 | inline comment should start with ‘# ‘ |
E265 | block comment should start with ‘# ‘ |
E266 | too many leading ‘#’ for block comment |
E271 | multiple spaces after keyword |
E272 | multiple spaces before keyword |
E273 | tab after keyword |
E274 | tab before keyword |
E275 | missing whitespace after keyword |
E3 | Blank line |
E301 | expected 1 blank line, found 0 |
E302 | expected 2 blank lines, found 0 |
E303 | too many blank lines (3) |
E304 | blank lines found after function decorator |
E305 | expected 2 blank lines after end of function or class |
E306 | expected 1 blank line before a nested definition |
E4 | Import |
E401 | multiple imports on one line |
E402 | module level import not at top of file |
E5 | Line length |
E501 (^) | line too long (82 > 79 characters) |
E502 | the backslash is redundant between brackets |
E7 | Statement |
E701 | multiple statements on one line (colon) |
E702 | multiple statements on one line (semicolon) |
E703 | statement ends with a semicolon |
E704 (*) | multiple statements on one line (def) |
E711 (^) | comparison to None should be ‘if cond is None:’ |
E712 (^) | comparison to True should be ‘if cond is True:’ or ‘if cond:’ |
E713 | test for membership should be ‘not in’ |
E714 | test for object identity should be ‘is not’ |
E721 (^) | do not compare types, use ‘isinstance()’ |
E722 | do not use bare except, specify exception instead |
E731 | do not assign a lambda expression, use a def |
E741 | do not use variables named ‘l’, ‘O’, or ‘I’ |
E742 | do not define classes named ‘l’, ‘O’, or ‘I’ |
E743 | do not define functions named ‘l’, ‘O’, or ‘I’ |
E9 | Runtime |
E901 | SyntaxError or IndentationError |
E902 | IOError |
W1 | Indentation warning |
W191 | indentation contains tabs |
W2 | Whitespace warning |
W291 | trailing whitespace |
W292 | no newline at end of file |
W293 | blank line contains whitespace |
W3 | Blank line warning |
W391 | blank line at end of file |
W5 | Line break warning |
W503 (*) | line break before binary operator |
W504 (*) | line break after binary operator |
W505 (*^) | doc line too long (82 > 79 characters) |
W6 | Deprecation warning |
W601 | .has_key() is deprecated, use ‘in’ |
W602 | deprecated form of raising exception |
W603 | ‘<>’ is deprecated, use ‘!=’ |
W604 | backticks are deprecated, use ‘repr()’ |
W605 | invalid escape sequence ‘x’ |
W606 | ‘async’ and ‘await’ are reserved keywords starting with Python 3.7 |
