PyLint features
1. Options
1.1. General options
rcfile
Specify a configuration file.
init-hook
Python code to execute, usually for sys.path manipulation such as pygtk.require().
errors-only
In error mode, checkers without error messages are disabled and for others, only the ERROR messages are displayed, and no reports are done by default
profile
Profiled execution.
ignore
Add <file or directory> to the black list. It should be a base name, not a path. You may set this option multiple times.
Default: CVS
persistent
Pickle collected data for later comparisons.
Default: yes
load-plugins
List of plugins (as comma separated values of python modules names) to load, usually to register additional checkers.
long-help
more verbose help.
1.2. Commands options
help-msg
Display a help message for the given message id and exit. The value may be a comma separated list of message ids.
list-msgs
Generate pylint's messages.
full-documentation
Generate pylint's full documentation.
generate-rcfile
Generate a sample configuration file according to the current configuration. You can put other options before this one to get them in the generated configuration.
generate-man
Generate pylint's man page.
1.3. Messages control options
enable
Enable the message, report, category or checker with the given id(s). You can either give multiple identifier separated by comma (,) or put this option multiple time.
disable
Disable the message, report, category or checker with the given id(s). You can either give multiple identifier separated by comma (,) or put this option multiple time (only on the command line, not in the configuration file where it should appear only once).
1.4. Reports options
output-format
Set the output format. Available formats are text, parseable, colorized, msvs (visual studio) and html
Default: text
include-ids
Include message's id in output
files-output
Put messages in a separate file for each module / package specified on the command line instead of printing them on stdout. Reports (if any) will be written in a file name "pylint_global.[txt|html]".
reports
Tells whether to display a full report or only the messages
Default: yes
evaluation
Python expression which should return a note less than 10 (10 is the highest note). You have access to the variables errors warning, statement which respectively contain the number of errors / warnings messages and the total number of statements analyzed. This is used by the global evaluation report (RP0004).
Default: 10.0 - ((float(5 * error + warning + refactor + convention) / statement) * 10)
comment
Add a comment according to your evaluation note. This is used by the global evaluation report (RP0004).
2. metrics checker
2.1. Reports
RP0701
Raw metrics
3. logging checker
3.1. Messages
W6501
Specify string format arguments as logging function parameters Used when a logging statement has a call form of "logging.<logging method>(format_string % (format_args...))". Such calls should leave string interpolation to the logging method itself and be written "logging.<logging method>(format_string, format_args...)" so that the program may avoid incurring the cost of the interpolation in those cases in which no message will be logged. For more, see http://www.python.org/dev/peps/pep-0282/.
4. similarities checker
4.1. Options
min-similarity-lines
Minimum lines number of a similarity.
Default: 4
ignore-comments
Ignore comments when computing similarities.
Default: yes
ignore-docstrings
Ignore docstrings when computing similarities.
Default: yes
4.2. Messages
R0801
Similar lines in %s files Indicates that a set of similar lines has been detected among multiple file. This usually means that the code should be refactored to avoid this duplication.
4.3. Reports
R0801
Duplication
5. string_format checker
5.1. Messages
E9900
Unsupported format character %r (%#02x) at index %d Used when a unsupported format character is used in a format string.
E9901
Format string ends in middle of conversion specifier Used when a format string terminates before the end of a conversion specifier.
E9902
Mixing named and unnamed conversion specifiers in format string Used when a format string contains both named (e.g. '%(foo)d') and unnamed (e.g. '%d') conversion specifiers. This is also used when a named conversion specifier contains * for the minimum field width and/or precision.
E9903
Expected mapping for format string, not %s Used when a format string that uses named conversion specifiers is used with an argument that is not a mapping.
E9904
Missing key %r in format string dictionary Used when a format string that uses named conversion specifiers is used with a dictionary that doesn't contain all the keys required by the format string.
E9905
Too many arguments for format string Used when a format string that uses unnamed conversion specifiers is given too few arguments.
E9906
Not enough arguments for format string Used when a format string that uses unnamed conversion specifiers is given too many arguments
W9900
Format string dictionary key should be a string, not %s Used when a format string that uses named conversion specifiers is used with a dictionary whose keys are not all strings.
W9901
Unused key %r in format string dictionary Used when a format string that uses named conversion specifiers is used with a dictionary that conWtains keys not required by the format string.
6. format checker
6.1. Options
max-line-length
Maximum number of characters on a single line.
Default: 80
max-module-lines
Maximum number of lines in a module
Default: 1000
indent-string
String used as indentation unit. This is usually " " (4 spaces) or "t" (1 tab).
Default: ' '
6.2. Messages
W0301
Unnecessary semicolon Used when a statement is ended by a semi-colon (";"), which isn't necessary (that's python, not C ;).
W0311
Bad indentation. Found %s %s, expected %s Used when an unexpected number of indentation's tabulations or spaces has been found.
W0312
Found indentation with %ss instead of %ss Used when there are some mixed tabs and spaces in a module.
W0331
Use of the <> operator Used when the deprecated "<>" operator is used instead of "!=".
W0332
Use l as long integer identifier Used when a lower case "l" is used to mark a long integer. You should use a upper case "L" since the letter "l" looks too much like the digit "1"
W0333
Use of the `` operator Used when the deprecated "``" (backtick) operator is used instead of the str() function.
C0301
Line too long (%s/%s) Used when a line is longer than a given number of characters.
C0302
Too many lines in module (%s) Used when a module has too much lines, reducing its readability.
C0321
More than one statement on a single line Used when more than on statement are found on the same line.
C0322
Operator not preceded by a space Used when one of the following operator (!= | <= | == | >= | < | > | = | += | -= | *= | /= | %) is not preceded by a space.
C0323
Operator not followed by a space Used when one of the following operator (!= | <= | == | >= | < | > | = | += | -= | *= | /= | %) is not followed by a space.
C0324
Comma not followed by a space Used when a comma (",") is not followed by a space.
F0321
Format detection error in %r Used when an unexpected error occurred in bad format detection.Please report the error if it occurs.
7. typecheck checker
7.1. Options
ignore-mixin-members
Tells whether missing members accessed in mixin class should be ignored. A mixin class is detected if its name ends with "mixin" (case insensitive).
Default: yes
ignored-classes
List of classes names for which member attributes should not be checked (useful for classes with attributes dynamically set).
Default: SQLObject
zope
When zope mode is activated, add a predefined set of Zope acquired attributes to generated-members.
generated-members
List of members which are set dynamically and missed by pylint inference system, and so shouldn't trigger E0201 when accessed.
Default: REQUEST,acl_users,aq_parent
7.2. Messages
E1101
%s %r has no %r member Used when a variable is accessed for an unexistent member.
E1102
%s is not callable Used when an object being called has been inferred to a non callable object
E1103
%s %r has no %r member (but some types could not be inferred) Used when a variable is accessed for an unexistent member, but astng was not able to interpret all possible types of this variable.
E1111
Assigning to function call which doesn't return Used when an assignment is done on a function call but the inferred function doesn't return anything.
E1120
No value passed for parameter %s in function call Used when a function call passes too few arguments.
E1121
Too many positional arguments for function call Used when a function call passes too many positional arguments.
E1122
Duplicate keyword argument %r in function call Used when a function call passes the same keyword argument multiple times.
E1123
Passing unexpected keyword argument %r in function call Used when a function call passes a keyword argument that doesn't correspond to one of the function's parameter names.
E1124
Multiple values passed for parameter %r in function call Used when a function call would result in assigning multiple values to a function parameter, one value from a positional argument and one from a keyword argument.
W1111
Assigning to function call which only returns None Used when an assignment is done on a function call but the inferred function returns nothing but None.
8. variables checker
8.1. Options
init-import
Tells whether we should check for unused import in __init__ files.
dummy-variables-rgx
A regular expression matching the beginning of the name of dummy variables (i.e. not used).
Default: _|dummy
additional-builtins
List of additional names supposed to be defined in builtins. Remember that you should avoid to define new builtins when possible.
8.2. Messages
E0601
Using variable %r before assignment Used when a local variable is accessed before it's assignment.
E0602
Undefined variable %r Used when an undefined variable is accessed.
E0611
No name %r in module %r Used when a name cannot be found in a module.
W0601
Global variable %r undefined at the module level Used when a variable is defined through the "global" statement but the variable is not defined in the module scope.
W0602
Using global for %r but no assignment is done Used when a variable is defined through the "global" statement but no assignment to this variable is done.
W0603
Using the global statement Used when you use the "global" statement to update a global variable. PyLint just try to discourage this usage. That doesn't mean you can not use it !
W0604
Using the global statement at the module level Used when you use the "global" statement at the module level since it has no effect
W0611
Unused import %s Used when an imported module or variable is not used.
W0612
Unused variable %r Used when a variable is defined but not used.
W0613
Unused argument %r Used when a function or method argument is not used.
W0614
Unused import %s from wildcard import Used when an imported module or variable is not used from a 'from X import *' style import.
Inline emphasis start-string without end-string.
W0621
Redefining name %r from outer scope (line %s) Used when a variable's name hide a name defined in the outer scope.
W0622
Redefining built-in %r Used when a variable or function override a built-in.
W0631
Using possibly undefined loop variable %r Used when an loop variable (i.e. defined by a for loop or a list comprehension or a generator expression) is used outside the loop.
9. miscellaneous checker
9.1. Options
notes
List of note tags to take in consideration, separated by a comma.
Default: FIXME,XXX,TODO
9.2. Messages
E0501
Non ascii characters found but no encoding specified (PEP 263) Used when some non ascii characters are detected but now encoding is specified, as explicited in the PEP 263.
E0502
Wrong encoding specified (%s) Used when a known encoding is specified but the file doesn't seem to be actually in this encoding.
W0511
Used when a warning note as FIXME or XXX is detected.
10. imports checker
10.1. Options
deprecated-modules
Deprecated modules which should not be used, separated by a comma
Default: regsub,string,TERMIOS,Bastion,rexec
import-graph
Create a graph of every (i.e. internal and external) dependencies in the given file (report RP0402 must not be disabled)
ext-import-graph
Create a graph of external dependencies in the given file (report RP0402 must not be disabled)
int-import-graph
Create a graph of internal dependencies in the given file (report RP0402 must not be disabled)
10.2. Messages
W0401
Wildcard import %s Used when from module import * is detected.
W0402
Uses of a deprecated module %r Used a module marked as deprecated is imported.
W0403
Relative import %r, should be %r Used when an import relative to the package directory is detected.
W0404
Reimport %r (imported line %s) Used when a module is reimported multiple times.
W0406
Module import itself Used when a module is importing itself.
W0410
__future__ import is not the first non docstring statement Python 2.5 and greater require __future__ import to be the first non docstring statement in the module.
R0401
Cyclic import (%s) Used when a cyclic import between two or more modules is detected.
F0401
Unable to import %r Used when pylint has been unable to import a module.
10.3. Reports
RP0401
External dependencies
RP0402
Modules dependencies graph
11. classes checker
11.1. Options
ignore-iface-methods
List of interface methods to ignore, separated by a comma. This is used for instance to not check methods defines in Zope's Interface base class.
Default: isImplementedBy,deferred,extends,names,namesAndDescriptions,queryDescriptionFor,getBases,getDescriptionFor,getDoc,getName,getTaggedValue,getTaggedValueTags,isEqualOrExtendedBy,setTaggedValue,isImplementedByInstancesOf,adaptWith,is_implemented_by
defining-attr-methods
List of method names used to declare (i.e. assign) instance attributes.
Default: __init__,__new__,setUp
11.2. Messages
E0202
An attribute inherited from %s hide this method Used when a class defines a method which is hidden by an instance attribute from an ancestor class.
E0203
Access to member %r before its definition line %s Used when an instance member is accessed before it's actually assigned.
E0211
Method has no argument Used when a method which should have the bound instance as first argument has no argument defined.
E0213
Method should have "self" as first argument Used when a method has an attribute different the "self" as first argument. This is considered as an error since this is a so common convention that you shouldn't break it!
E0221
Interface resolved to %s is not a class Used when a class claims to implement an interface which is not a class.
E0222
Missing method %r from %s interface Used when a method declared in an interface is missing from a class implementing this interface
W0201
Attribute %r defined outside __init__ Used when an instance attribute is defined outside the __init__ method.
W0211
Static method with %r as first argument Used when a static method has "self" or "cls" as first argument.
W0212
Access to a protected member %s of a client class Used when a protected member (i.e. class member with a name beginning with an underscore) is access outside the class or a descendant of the class where it's defined.
W0221
Arguments number differs from %s method Used when a method has a different number of arguments than in the implemented interface or in an overridden method.
W0222
Signature differs from %s method Used when a method signature is different than in the implemented interface or in an overridden method.
W0223
Method %r is abstract in class %r but is not overridden Used when an abstract method (i.e. raise NotImplementedError) is not overridden in concrete class.
W0231
__init__ method from base class %r is not called Used when an ancestor class method has an __init__ method which is not called by a derived class.
W0232
Class has no __init__ method Used when a class has no __init__ method, neither its parent classes.
W0233
__init__ method from a non direct base class %r is called Used when an __init__ method is called on a class which is not in the direct ancestors for the analysed class.
R0201
Method could be a function Used when a method doesn't use its bound instance, and so could be written as a function.
C0202
Class method should have "cls" as first argument Used when a class method has an attribute different than "cls" as first argument, to easily differentiate them from regular instance methods.
C0203
Metaclass method should have "mcs" as first argument Used when a metaclass method has an attribute different the "mcs" as first argument.
F0202
Unable to check methods signature (%s / %s) Used when PyLint has been unable to check methods signature compatibility for an unexpected reason. Please report this kind if you don't make sense of it.
F0220
failed to resolve interfaces implemented by %s (%s) Used when a PyLint as failed to find interfaces implemented by a class
12. design checker
12.1. Options
max-args
Maximum number of arguments for function / method
Default: 5
ignored-argument-names
Argument names that match this expression will be ignored. Default to name with leading underscore
Default: _.*
max-locals
Maximum number of locals for function / method body
Default: 15
max-returns
Maximum number of return / yield for function / method body
Default: 6
max-branchs
Maximum number of branch for function / method body
Default: 12
max-statements
Maximum number of statements in function / method body
Default: 50
max-parents
Maximum number of parents for a class (see R0901).
Default: 7
max-attributes
Maximum number of attributes for a class (see R0902).
Default: 7
min-public-methods
Minimum number of public methods for a class (see R0903).
Default: 2
max-public-methods
Maximum number of public methods for a class (see R0904).
Default: 20
12.2. Messages
R0901
Too many ancestors (%s/%s) Used when class has too many parent classes, try to reduce this to get a more simple (and so easier to use) class.
R0902
Too many instance attributes (%s/%s) Used when class has too many instance attributes, try to reduce this to get a more simple (and so easier to use) class.
R0903
Too few public methods (%s/%s) Used when class has too few public methods, so be sure it's really worth it.
R0904
Too many public methods (%s/%s) Used when class has too many public methods, try to reduce this to get a more simple (and so easier to use) class.
R0911
Too many return statements (%s/%s) Used when a function or method has too many return statement, making it hard to follow.
R0912
Too many branches (%s/%s) Used when a function or method has too many branches, making it hard to follow.
R0913
Too many arguments (%s/%s) Used when a function or method takes too many arguments.
R0914
Too many local variables (%s/%s) Used when a function or method has too many local variables.
R0915
Too many statements (%s/%s) Used when a function or method has too many statements. You should then split it in smaller functions / methods.
R0921
Abstract class not referenced Used when an abstract class is not used as ancestor anywhere.
R0922
Abstract class is only referenced %s times Used when an abstract class is used less than X times as ancestor.
R0923
Interface not implemented Used when an interface class is not implemented anywhere.
13. basic checker
13.1. Options
module-rgx
Regular expression which should only match correct module names
Default: (([a-z_][a-z0-9_]*)|([A-Z][a-zA-Z0-9]+))$
const-rgx
Regular expression which should only match correct module level names
Default: (([A-Z_][A-Z0-9_]*)|(__.*__))$
class-rgx
Regular expression which should only match correct class names
Default: [A-Z_][a-zA-Z0-9]+$
function-rgx
Regular expression which should only match correct function names
Default: [a-z_][a-z0-9_]{2,30}$
method-rgx
Regular expression which should only match correct method names
Default: [a-z_][a-z0-9_]{2,30}$
attr-rgx
Regular expression which should only match correct instance attribute names
Default: [a-z_][a-z0-9_]{2,30}$
argument-rgx
Regular expression which should only match correct argument names
Default: [a-z_][a-z0-9_]{2,30}$
variable-rgx
Regular expression which should only match correct variable names
Default: [a-z_][a-z0-9_]{2,30}$
inlinevar-rgx
Regular expression which should only match correct list comprehension / generator expression variable names
Default: [A-Za-z_][A-Za-z0-9_]*$
good-names
Good variable names which should always be accepted, separated by a comma
Default: i,j,k,ex,Run,_
bad-names
Bad variable names which should always be refused, separated by a comma
Default: foo,bar,baz,toto,tutu,tata
no-docstring-rgx
Regular expression which should only match functions or classes name which do not require a docstring
Default: __.*__
required-attributes
Required attributes for module, separated by a comma
bad-functions
List of builtins function names that should not be used, separated by a comma
Default: map,filter,apply,input
13.2. Messages
E0100
__init__ method is a generator Used when the special class method __init__ is turned into a generator by a yield in its body.
E0101
Explicit return in __init__ Used when the special class method __init__ has an explicit return value.
E0102
%s already defined line %s Used when a function / class / method is redefined.
E0103
%r not properly in loop Used when break or continue keywords are used outside a loop.
E0104
Return outside function Used when a "return" statement is found outside a function or method.
E0105
Yield outside function Used when a "yield" statement is found outside a function or method.
E0106
Return with argument inside generator Used when a "return" statement with an argument is found outside in a generator function or method (e.g. with some "yield" statements).
E0107
Use of the non-existent %s operator Used when you attempt to use the C-style pre-increment orpre-decrement operator -- and ++, which doesn't exist in Python.
W0101
Unreachable code Used when there is some code behind a "return" or "raise" statement, which will never be accessed.
W0102
Dangerous default value %s as argument Used when a mutable value as list or dictionary is detected in a default value for an argument.
W0104
Statement seems to have no effect Used when a statement doesn't have (or at least seems to) any effect.
W0105
String statement has no effect Used when a string is used as a statement (which of course has no effect). This is a particular case of W0104 with its own message so you can easily disable it if you're using those strings as documentation, instead of comments.
W0107
Unnecessary pass statement Used when a "pass" statement that can be avoided is encountered.)
W0108
Lambda may not be necessary Used when the body of a lambda expression is a function call on the same argument list as the lambda itself; such lambda expressions are in all but a few cases replaceable with the function being called in the body of the lambda.
W0109
Duplicate key %r in dictionary Used when a dictionary expression binds the same key multiple times.
W0122
Use of the exec statement Used when you use the "exec" statement, to discourage its usage. That doesn't mean you can not use it !
W0141
Used builtin function %r Used when a black listed builtin function is used (see the bad-function option). Usual black listed functions are the ones like map, or filter , where Python offers now some cleaner alternative like list comprehension.
W0142
Used * or * magic* Used when a function or method is called using *args or **kwargs to dispatch arguments. This doesn't improve readability and should be used with care.
W0150
%s statement in finally block may swallow exception Used when a break or a return statement is found inside the finally clause of a try...finally block: the exceptions raised in the try clause will be silently swallowed instead of being re-raised.
W0199
Assert called on a 2-uple. Did you mean 'assert x,y'? A call of assert on a tuple will always evaluate to true if the tuple is not empty, and will always evaluate to false if it is.
C0102
Black listed name "%s" Used when the name is listed in the black list (unauthorized names).
C0103
Invalid name "%s" (should match %s) Used when the name doesn't match the regular expression associated to its type (constant, variable, class...).
C0111
Missing docstring Used when a module, function, class or method has no docstring. Some special methods like __init__ doesn't necessary require a docstring.
C0112
Empty docstring Used when a module, function, class or method has an empty docstring (it would be too easy ;).
C0121
Missing required attribute "%s" Used when an attribute required for modules is missing.
13.3. Reports
RP0101
Statistics by type
14. exceptions checker
14.1. Messages
E0701
Bad except clauses order (%s) Used when except clauses are not in the correct order (from the more specific to the more generic). If you don't fix the order, some exceptions may not be catched by the most specific handler.
E0702
Raising %s while only classes, instances or string are allowed Used when something which is neither a class, an instance or a string is raised (i.e. a TypeError will be raised).
E0710
Raising a new style class which doesn't inherit from BaseException Used when a new style class which doesn't inherit from BaseException is raised since it's not possible with python >= 2.5.
E0711
NotImplemented raised - should raise NotImplementedError Used when NotImplemented is raised instead of NotImplementedError
W0701
Raising a string exception Used when a string exception is raised.
W0702
No exception type(s) specified Used when an except clause doesn't specify exceptions type to catch.
W0703
Catch "Exception" Used when an except catches Exception instances.
W0704
Except doesn't do anything Used when an except clause does nothing but "pass" and there is no "else" clause.
W0710
Exception doesn't inherit from standard "Exception" class Used when a custom exception class is raised but doesn't inherit from the builtin "Exception" class.
15. newstyle checker
15.1. Messages
E1001
Use __slots__ on an old style class Used when an old style class use the __slots__ attribute.
E1002
Use super on an old style class Used when an old style class use the super builtin.
E1003
Bad first argument %r given to super class Used when another argument than the current class is given as first argument of the super builtin.
W1001
Use of "property" on an old style class Used when PyLint detect the use of the builtin "property" on an old style class while this is relying on new style classes features