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Python PEP8 code specification common problems and solutions
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1: Introduction to Python’s EP8 code specification P
Therefore, record common PEP8 code specification problems and solutions, study them, and continue to update when you encounter them, develop good habits, and write standardized code!
PEP 8: no newline at end of file
Solution: You need to start a new line at the end of the code, just move the cursor to the end and press EnterPEP 8: indentation is not a multiple of four
Solution: Indentation is not a multiple of 4, check the indentationPEP 8: over-indented
Solution: excessive indentation, check the indentationPEP 8: missing whitespace after','
Solution: There is a missing space after the comma, just add a space, similar to a missing space after a semicolon or colonPEP 8: multiple imports on one line
Solution: Do not reference multiple libraries in one import sentence. For example: import socket, urllib.error is best written as: import socket import urllib.errorPEP 8: blank line at end of line
Solution: There are too many spaces at the end of the line of code, just delete the spacesPEP 8: at least two spaces before inline comment
Solution: There must be at least two spaces between code and commentsPEP 8: block comment should start with '#'
Solution: The comment should start with # plus a spacePEP 8: inline comment should start with '#'
Solution: The comment should start with # plus a spacePEP 8: module level import not at top of file
Solution: import is not at the top of the file, there may be other code before itPEP 8: expected 2 blank lines, found 0
Solution: Two blank lines are needed, just add two blank linesPEP 8: function name should be lowercase
Solution: Just change the function name to lowercasePEP 8: missing whitespace around operator
Solution: There are missing spaces before and after operators ('=', '>', '<', etc.), just add themPEP 8: unexpected spaces around keyword / parameter equals
Solution: Unexpected spaces appear around the keyword / parameter equals sign, just remove the spacesPEP 8: multiple statements on one line (colon)
Solution: Multi-line statements are written on one line, for example: if x == 2: print('OK') should be written in two linesPEP 8: line too long (82 > 79 characters)
Solution: The maximum length limit of 79 per line is exceededPEP 8: Simplify chained comparison
can simplify chained comparison (for example: if a >= 0 and a <= 9: can be abbreviated as: if 0 <= a <= 9:)If you want to selectively ignore the warning messages of PEP8 coding style, you can use the following method: (Develop good habits and write standardized code! Ignoring is not recommended!)
① Move the mouse to the area where the warning message appears, press alt+Enter, and choose to ignore the error:
②Select File - Settings - Editor - Inspections, find the PEP8 coding style violation option under Python, click the plus sign in Ignore errors in the lower right corner to add the warning message ID that needs to be ignored (see the appendix below for ID information), for example Ignore the warning that identification contains mixed spaces and tabs, just add its ID: E101
Appendix: All warning messages and corresponding IDs, official address: 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
2: PEP 8: E101 indentation contains mixed spaces and tabs solution
As shown in the picture above, due to the irregular indentation, the PyCharm tool automatically recognizes that the indentation contains multiple spaces or tabs, resulting in non-compliance with EP8 code specifications. Warning message: PEP 8: E101 indentation contains mixed spaces and tabs
There are usually two solutions:
2.1: The code in the underlined part is indented by one tab stop, or two tab stops:
2.2: file-->setting-->enter PEP 8 in the search box, and then remove the two check boxes pointed by the arrows in the picture below--->Confirm
