A list of pylint-errors with reasoning and examples of erroneous and correct code.

Table of contents

• CLI usage
  • Stable release
  • Dev builds
• List of errors

CLI usage

It's not required to install CLI util as long as you can navigate list of errors here or on this web-site but you may want to do so.

Stable release

You can install a stable release simply by such commands:

$ python3 -m pip install plerr
$ plerr r1710

For pipx:

$ python3 -m pip install pipx # if not yet installed pipx
$ python3 -m pipx ensurepath # ensure directory where pipx stores apps is on PATH
$ pipx install plerr
$ plerr r1710

Dev builds

In order to use development plerr builds you need to invoke the following commands:

$ git clone https://github.com/sprytnyk/pylint-errors.git
$ sudo apt update && sudo apt install -y python3-pip # if not yet installed
$ cd pylint-errors
$ python3 setup.py test
$ python3 setup.py install --user
$ python3 -m plerr r1710

pipx users may install the library by such commands:

$ git clone https://github.com/sprytnyk/pylint-errors.git
$ sudo apt install -y make python3-pip python3-venv # if not yet installed
$ cd pylint-errors
$ python3 -m pip install pipx wheel # install a package to build a wheel and pipx
$ python3 -m pipx ensurepath # ensure directory where pipx stores apps is on PATH
$ python3 setup.py test # run tests
$ make clean
$ python3 setup.py bdist_wheel # build a binary wheel
$ pipx install dist/* # install a binary wheel by pipx
$ plerr r1710

In order to get the latest updates just git pull origin master and invoke a command in the root of the project (sudo apt install make if not yet installed) make rai to install to Python 3 user space site packages or make raip for pipx.

List of errors

Error codes with [+] mean they've got examples of bad and good code. Rationalisation provided for all entries.

Async Checker Messages

• E1700 (yield-inside-async-function) [+]
• E1701 (not-async-context-manager) [+]

Basic Checker Messages

• C0102 (blacklisted-name) [+]
• C0103 (invalid-name) [+]
• C0112 (empty-docstring) [+]
• C0114 (missing-module-docstring) [+]
• C0115 (missing-class-docstring) [+]
• C0116 (missing-function-docstring) [+]
• C0121 (singleton-comparison) [+]
• C0122 (misplaced-comparison-constant) [+]
• C0123 (unidiomatic-typecheck) [+]
• E0100 (init-is-generator) [+]
• E0101 (return-in-init) [+]
• E0102 (function-redefined) [+]
• E0103 (not-in-loop) [+]
• E0104 (return-outside-function) [+]
• E0105 (yield-outside-function) [+]
• E0106 (return-arg-in-generator)
• E0107 (nonexistent-operator) [+]
• E0108 (duplicate-argument-name) [+]
• E0110 (abstract-class-instantiated) [+]
• E0111 (bad-reversed-sequence) [+]
• E0112 (too-many-star-expressions) [+]
• E0113 (invalid-star-assignment-target) [+]
• E0114 (star-needs-assignment-target) [+]
• E0115 (nonlocal-and-global) [+]
• E0116 (continue-in-finally) [+]
• E0117 (nonlocal-without-binding) [+]
• E0118 (used-prior-global-declaration) [+]
• E0119 (misplaced-format-function) [+]
• R0123 (literal-comparison) [+]
• R0124 (comparison-with-itself) [+]
• W0101 (unreachable) [+]
• W0102 (dangerous-default-value) [+]
• W0104 (pointless-statement) [+]
• W0105 (pointless-string-statement) [+]
• W0106 (expression-not-assigned) [+]
• W0107 (unnecessary-pass) [+]
• W0108 (unnecessary-lambda) [+]
• W0109 (duplicate-key) [+]
• W0111 (assign-to-new-keyword) [+]
• W0120 (useless-else-on-loop) [+]
• W0122 (exec-used) [+]
• W0123 (eval-used) [+]
• W0124 (confusing-with-statement) [+]
• W0125 (using-constant-test)
• W0126 (missing-parentheses-for-call-in-test)
• W0127 (self-assigning-variable) [+]
• W0128 (redeclared-assigned-name)
• W0143 (comparison-with-callable) [+]
• W0150 (lost-exception) [+]
• W0199 (assert-on-tuple) [+]

Broad Try Clause Checker Messages

• W0717 (too-many-try-statements)

Classes Checker Messages

• C0202 (bad-classmethod-argument) [+]
• C0203 (bad-mcs-method-argument) [+]
• C0204 (bad-mcs-classmethod-argument) [+]
• C0205 (single-string-used-for-slots) [+]
• E0202 (method-hidden) [+]
• E0203 (access-member-before-definition) [+]
• E0211 (no-method-argument) [+]
• E0213 (no-self-argument) [+]
• E0236 (invalid-slots-object) [+]
• E0237 (assigning-non-slot) [+]
• E0238 (invalid-slots) [+]
• E0239 (inherit-non-class) [+]
• E0240 (inconsistent-mro) [+]
• E0241 (duplicate-bases) [+]
• E0242 (class-variable-slots-conflict) [+]
• E0301 (non-iterator-returned) [+]
• E0302 (unexpected-special-method-signature) [+]
• E0303 (invalid-length-returned) [+]
• F0202 (method-check-failed)
• R0201 (no-self-use) [+]
• R0202 (no-classmethod-decorator) [+]
• R0203 (no-staticmethod-decorator) [+]
• R0205 (useless-object-inheritance) [+]
• R0206 (property-with-parameters) [+]
• W0201 (attribute-defined-outside-init) [+]
• W0211 (bad-staticmethod-argument) [+]
• W0212 (protected-access) [+]
• W0221 (arguments-differ) [+]
• W0222 (signature-differs)
• W0223 (abstract-method) [+]
• W0231 (super-init-not-called) [+]
• W0232 (no-init) [+]
• W0233 (non-parent-init-called) [+]
• W0235 (useless-super-delegation) [+]
• W0236 (invalid-overridden-method) [+]

Compare-To-Empty-String Checker Messages

• C1901 (compare-to-empty-string) [+]

Compare-To-Zero Checker Messages

• C2001 (compare-to-zero) [+]

Deprecated Builtins Checker Messages

• W0141 (bad-builtin) [+]

Design Checker Messages

• R0901 (too-many-ancestors) [+]
• R0902 (too-many-instance-attributes) [+]
• R0903 (too-few-public-methods) [+]
• R0904 (too-many-public-methods) [+]
• R0911 (too-many-return-statements) [+]
• R0912 (too-many-branches) [+]
• R0913 (too-many-arguments) [+]
• R0914 (too-many-locals) [+]
• R0915 (too-many-statements) [+]
• R0916 (too-many-boolean-expressions) [+]
• R1260 (too-complex) [+]

Docstyle Checker Messages

• C0198 (bad-docstring-quotes) [+]
• C0199 (docstring-first-line-empty) [+]

Else If Used Checker Messages

• R5501 (else-if-used) [+]

Exceptions Checker Messages

• E0701 (bad-except-order) [+]
• E0702 (raising-bad-type) [+]
• E0703 (bad-exception-context) [+]
• E0704 (misplaced-bare-raise) [+]
• E0710 (raising-non-exception) [+]
• E0711 (notimplemented-raised) [+]
• E0712 (catching-non-exception) [+]
• W0702 (bare-except) [+]
• W0703 (broad-except) [+]
• W0705 (duplicate-except) [+]
• W0706 (try-except-raise) [+]
• W0707 (raise-missing-from) [+]
• W0711 (binary-op-exception) [+]
• W0715 (raising-format-tuple) [+]
• W0716 (wrong-exception-operation) [+]

Format Checker Messages

• C0301 (line-too-long) [+]
• C0302 (too-many-lines)
• C0303 (trailing-whitespace) [+]
• C0304 (missing-final-newline)
• C0305 (trailing-newlines)
• C0321 (multiple-statements) [+]
• C0325 (superfluous-parens) [+]
• C0326 (bad-whitespace) [+]
• C0327 (mixed-line-endings)
• C0328 (unexpected-line-ending-format)
• C0330 (bad-continuation)
• W0301 (unnecessary-semicolon) [+]
• W0311 (bad-indentation) [+]
• W0312 (mixed-indentation)

Imports Checker Messages

• C0410 (multiple-imports) [+]
• C0411 (wrong-import-order) [+]
• C0412 (ungrouped-imports) [+]
• C0413 (wrong-import-position) [+]
• C0414 (useless-import-alias) [+]
• C0415 (import-outside-toplevel) [+]
• E0401 (import-error) [+]
• E0402 (relative-beyond-top-level) [+]
• R0401 (cyclic-import) [+]
• W0401 (wildcard-import) [+]
• W0402 (deprecated-module) [+]
• W0404 (reimported) [+]
• W0406 (import-self) [+]
• W0407 (preferred-module) [+]
• W0410 (misplaced-future) [+]

Logging Checker Messages

• E1200 (logging-unsupported-format)
• E1201 (logging-format-truncated) [+]
• E1205 (logging-too-many-args)
• E1206 (logging-too-few-args)
• W1201 (logging-not-lazy) [+]
• W1202 (logging-format-interpolation) [+]

Miscellaneous Checker Messages

• I0023 (use-symbolic-message-instead)
• W0511 (fixme) [+]

Multiple Types Checker Messages

• R0204 (redefined-variable-type)

Newstyle Checker Messages

• E1003 (bad-super-call) [+]

Overlap-Except Checker Messages

• W0714 (overlapping-except)

Parameter Documentation Checker Messages

• W9005 (multiple-constructor-doc) [+]
• W9006 (missing-raises-doc) [+]
• W9008 (redundant-returns-doc)
• W9010 (redundant-yields-doc)
• W9011 (missing-return-doc) [+]
• W9012 (missing-return-type-doc) [+]
• W9013 (missing-yield-doc)
• W9014 (missing-yield-type-doc)
• W9015 (missing-param-doc) [+]
• W9016 (missing-type-doc) [+]
• W9017 (differing-param-doc) [+]
• W9018 (differing-type-doc) [+]

Refactoring Checker Messages

• C0113 (unneeded-not) [+]
• C0200 (consider-using-enumerate) [+]
• C0201 (consider-iterating-dictionary) [+]
• C1801 (len-as-condition) [+]
• R1701 (consider-merging-isinstance)
• R1702 (too-many-nested-blocks)
• R1703 (simplifiable-if-statement) [+]
• R1704 (redefined-argument-from-local) [+]
• R1705 (no-else-return) [+]
• R1706 (consider-using-ternary)
• R1707 (trailing-comma-tuple) [+]
• R1708 (stop-iteration-return) [+]
• R1709 (simplify-boolean-expression)
• R1710 (inconsistent-return-statements) [+]
• R1711 (useless-return) [+]
• R1712 (consider-swap-variables) [+]
• R1713 (consider-using-join) [+]
• R1714 (consider-using-in) [+]
• R1715 (consider-using-get)
• R1716 (chained-comparison) [+]
• R1717 (consider-using-dict-comprehension)
• R1718 (consider-using-set-comprehension)
• R1719 (simplifiable-if-expression) [+]
• R1720 (no-else-raise) [+]
• R1721 (unnecessary-comprehension) [+]
• R1722 (consider-using-sys-exit) [+]
• R1723 (no-else-break) [+]
• R1724 (no-else-continue) [+]

Similarities Checker Messages

• R0801 (duplicate-code)

Spelling Checker Messages

• C0401 (wrong-spelling-in-comment)
• C0402 (wrong-spelling-in-docstring)
• C0403 (invalid-characters-in-docstring)

Stdlib Checker Messages

• E1507 (invalid-envvar-value) [+]
• W1501 (bad-open-mode) [+]
• W1502 (boolean-datetime)
• W1503 (redundant-unittest-assert) [+]
• W1505 (deprecated-method)
• W1506 (bad-thread-instantiation) [+]
• W1507 (shallow-copy-environ) [+]
• W1508 (invalid-envvar-default) [+]
• W1509 (subprocess-popen-preexec-fn) [+]
• W1510 (subprocess-run-check) [+]

String Checker Messages

• E1300 (bad-format-character) [+]
• E1301 (truncated-format-string)
• E1302 (mixed-format-string) [+]
• E1303 (format-needs-mapping)
• E1304 (missing-format-string-key) [+]
• E1305 (too-many-format-args) [+]
• E1306 (too-few-format-args) [+]
• E1307 (bad-string-format-type) [+]
• E1310 (bad-str-strip-call)
• W1300 (bad-format-string-key)
• W1301 (unused-format-string-key)
• W1302 (bad-format-string) [+]
• W1303 (missing-format-argument-key) [+]
• W1304 (unused-format-string-argument) [+]
• W1305 (format-combined-specification) [+]
• W1306 (missing-format-attribute) [+]
• W1307 (invalid-format-index) [+]
• W1308 (duplicate-string-formatting-argument)
• W1401 (anomalous-backslash-in-string)
• W1402 (anomalous-unicode-escape-in-string) [+]
• W1403 (implicit-str-concat-in-sequence)

Typecheck Checker Messages

• E1101 (no-member) [+]
• E1102 (not-callable) [+]
• E1111 (assignment-from-no-return) [+]
• E1120 (no-value-for-parameter) [+]
• E1121 (too-many-function-args) [+]
• E1123 (unexpected-keyword-arg) [+]
• E1124 (redundant-keyword-arg) [+]
• E1125 (missing-kwoa)
• E1126 (invalid-sequence-index) [+]
• E1127 (invalid-slice-index) [+]
• E1128 (assignment-from-none) [+]
• E1129 (not-context-manager) [+]
• E1130 (invalid-unary-operand-type) [+]
• E1131 (unsupported-binary-operation) [+]
• E1132 (repeated-keyword)
• E1133 (not-an-iterable) [+]
• E1134 (not-a-mapping)
• E1135 (unsupported-membership-test) [+]
• E1136 (unsubscriptable-object) [+]
• E1137 (unsupported-assignment-operation) [+]
• E1138 (unsupported-delete-operation) [+]
• E1139 (invalid-metaclass)
• E1140 (unhashable-dict-key) [+]
• E1141 (dict-iter-missing-items) [+]
• I1101 (c-extension-no-member)
• W1113 (keyword-arg-before-vararg) [+]
• W1114 (arguments-out-of-order)

Variables Checker Messages

• E0601 (used-before-assignment) [+]
• E0602 (undefined-variable)
• E0603 (undefined-all-variable) [+]
• E0604 (invalid-all-object) [+]
• E0611 (no-name-in-module) [+]
• E0633 (unpacking-non-sequence) [+]
• W0601 (global-variable-undefined) [+]
• W0602 (global-variable-not-assigned) [+]
• W0603 (global-statement) [+]
• W0604 (global-at-module-level) [+]
• W0611 (unused-import) [+]
• W0612 (unused-variable) [+]
• W0613 (unused-argument) [+]
• W0614 (unused-wildcard-import) [+]
• W0621 (redefined-outer-name) [+]
• W0622 (redefined-builtin) [+]
• W0623 (redefine-in-handler)
• W0631 (undefined-loop-variable) [+]
• W0632 (unbalanced-tuple-unpacking) [+]
• W0640 (cell-var-from-loop) [+]
• W0641 (possibly-unused-variable)
• W0642 (self-cls-assignment)