Frequently Asked Questions / Usage tips for PyLint
Author: Logilab
Keywords: logilab

| Frequently Asked Questions / Usage tips for PyLint

| Frequently Asked Questions / Usage tips for PyLint Question: Is it possible to give file as argument to pylint, instead of module ? Answer: pylint expects the name of a package or module as argument. As a convenience, you can give to it a file name if it's possible to guess a module name from the file's path, using the python path. Some examples : "pylint mymodule.py" should always works since the current working directory is automatically added on top of the python path "pylint directory/mymodule.py" will work if "directory" is a python package (i.e. has an __init__.py file) or if "directory" is in the python path. "pylint /whatever/directory/mymodule.py" will work if either: "/whatever/directory" is in the python path your cwd is "/whatever/directory" "directory" is a python package and "/whatever" is in the python path "directory" is a python package and your cwd is "/whatever" and so on... Question: I'm using psyobj from psyco and get a lot of spurious "unused variables messages". Is it normal ? Answer: Yes. That's actually due to a bug in psyco, making the locals() function for objects inheriting from psyobj returning an empty dictionary. For the moment, the only way to fix this is to use the PYLINT_IMPORT environment variable to not use psyco during pylint checking. Sample code import os try: if os.environ.has_key('PYLINT_IMPORT'): raise ImportError() from psyco.classes import psyobj except ImportError: class psyobj: pass NOTICE: this problem should not occurs with pylint >= 0.5 since from this version pylint is not looking anymore for information in living objects (i.e. it doesn't anymore import analysed modules) Question: I've a function / method which is a callback where I do not have any control on received argument, and pylint is complaining about unused arguments. What can I do to avoid those warnings ? Answer: prefix (ui) the callback's name by cb_, as in cb_onclick(...). By doing so arguments usage won't be checked. Another solution is to use one of the name defined in the "dummy-variables" configuration variable for unused argument ("_" and "dummy" by default). Question: When is pylint considering a class as an interface ? Answer: A class is considered as an interface if there is a class named "Interface" somewhere in it ancestor's tree. Question: When is pylint considering that a class is implementing a given interface ? Answer: Pylint is using the Zope 2 interfaces conventions, and so is considering that a class is implementing interfaces listed in its __implements__ attribute. Question: When is pylint considering a class as an abstract class ? Answer: A class is considered as an abstract class if at least one of its methods is doing nothing but raising NotImplementedError Question: Is there some way to disable some message for a particular module only ? Answer: Yes, you can disable or enable (globally disabled) message at the module level by adding the corresponding option in a comment at the top of the file: # pylint: disable-msg=W0401, E0202 # pylint: enable-msg=C0302 Question: I have a mixin class relying on attributes of the mixed class, and I would like to not have the "access to undefined member" message on this class. Is it possible ? Answer: Yes :o) To do so you have to set the ignore-mixin-members option to "yes" (this is the default value) and to name your mixin class with a name which ends with "mixin" (whatever case) Question: Is it possible to locally disable a particular message for a block of code or for a single line of code ? Answer: Yes, this feature has been added in pylint 0.11. This may be done by adding "#pylint: disable-msg=W0123,E4567" at the desired block level or at the end of the desired line of code Question: Where is the persistent data stored to make comparison between two successive runs ? Answer: Analysis data are stored as pickle file in a directory which is localized using the following rules: value of the PYLINTHOME environment variable if set ".pylint.d" subdirectory of the user's home directory if it is found (not always findable on Windows platforms) ".pylint.d" directory in the current directory Question: How can I know the option name (for pylintrc) corresponding to a specific command line option ? Answer: You can always generate a sample pylintrc file with --generate-rcfile Every option present on the command line before this will be included in the rc file For example: pylint --disable-msg=W0702,C0103 --class-rgx='[A-Z][a-z]+' --generate-rcfile Question: pychecker has no problem finding the imports and reporting on problems with them, while pylint seems unable to deal with the same imports. Why ? Answer: pychecker and pylint use different approaches. pychecker imports the modules and rummages around in the result, hence it sees my mangled sys.path. pylint doesn't import any of the candidate modules and thus doesn't include any of import's side effects (good and bad). It traverses an AST representation of the code.