Use pylint to lint check all examples

[tannewt]

It enforces pep8: https://github.com/PyCQA/pycodestyle

[tannewt]

We do this in libraries already and should follow the example settings there: https://github.com/adafruit/cookiecutter-adafruit-circuitpython/blob/master/%7B%7B%20cookiecutter.library_name%20%7D%7D/.travis.yml#L30

[craigargh]

I'm going to work on:

• ufo
• Trinket_Ultrasonic_Rangefinder
• Trinket_Gemma_Space_Invader_Pendant
• Trinket_Gemma_Servo_Control
• Trinket_Gemma_Mini_Theramin

[ladyada]

one possible route - have the pylint script live in the root of the repo, and run on any .py script it finds, UNLESS a .circuitpython.skip file exists in the same directory of the .py script

[dylwhich]

I'm working on adding a pylint script and a travis-ci config to run it

[craigargh]

@dylwhich Would you be able to add a pylint config file as well?

[craigargh]

I'm using the following to run pylint

pylint --disable=missing-docstring,invalid-name,bad-whitespace,duplicate-code,import-error,consider-using-enumerate,no-name-in-module,no-member,too-many-arguments,no-else-return */*.py

It might make sense to Flake8 instead of PyLint as it's less opinionated.

[craigargh]

This is the final version of the pylint setup that I'm using

pylint --disable=missing-docstring,invalid-name,bad-whitespace,duplicate-code,import-error,consider-using-enumerate,no-name-in-module,no-member,too-many-arguments,no-else-return,simplifiable-if-statement,global-statement,anomalous-backslash-in-string,too-many-locals,too-many-statements,no-self-use,protected-access,len-as-condition,too-many-instance-attributes,too-few-public-methods,eval-used,redefined-outer-name,broad-except --msg-template='{path} {line}: {msg} ({symbol})' */*.py 

I'll try to explain each of the checks I've disabled in another message.

[craigargh]

• duplicate-code: Each of the examples is a self-contained project so having shared code between them doesn't make sense.
• import-error: The Circuit Python specific libraries can't be installed/imported in a standard Python installation
• consider-using-enumerate: A lot of code uses for index in range(len(values_list)): ..., using enumerate instead would require a lot of refactoring that I don't have the time to test.
• no-name-in-module: This is related to the import-error
• no-member: This is related to the import-error
• too-many-arguments: This will complain if there are more than 5 arguments in a function. Only 3D_Printed_LED_Microphone_Flag and Logans_Run_Hand_Jewel_LED have this issue.
• no-else-return: This stops use of else when the if/elif block have a return statement. I think it is clearer/more consistent to leave in the else block.
• simplifiable-if-statement: This checks for code like if button == True: led = True; else: led = False. Although this could be simplified to led = button, I think the original version is easier to understand for beginners.
• global-statement: Doesn't like the use of global var_name in functions. Code could be refactored to remove this
• anomalous-backslash-in-string: This doesn't like backslashes in strings that aren't used as escape characters.
• too-many-locals: This happens when a function has a lot of variables. These functions could be refactored to reduce their length
• too-many-statements: Same as above, this happens when a function a lot of lines. These functions could be refactored to reduce their length
• no-self-use: Methods in classes that could be static functions as they don't use the self argument. Can be quickly fixed with @staticmethod annotation, however I wasn't sure if this was implemented in CircuitPython
• protected-access: Raised when code accesses protected attributes of a class (i.e. methods beginning with two underscores). Could be fixed by changing methods to have one or zero underscores at the start.
• len-as-condition: This happens for if statements that check the length of a list is 0 if len(values) == 0: .... This could be replaced with if values:, however I think the longer version is easier to understand for beginners.
• too-many-instance-attributes: Classes that have a lot of attributes
• too-few-public-methods: Classes that have 0~2 methods
• eval-used: I would remove the use of eval, however I didn't want to refactor without testing.
• redefined-outer-name: Variables in functions that have the same name as variables in the global scope. I've fixed this in a lot of places, however there were some bits of code I didn't understand the code enough to change it.
• broad-except: This doesn't like the use of except Exception:.... I didn't know what error was expected to be thrown so I left it as is.
• --msg-template='{path} {line}: {msg} ({symbol})' */*.py: For an unknown reason some pylint errors weren't listed next to the correct file that they were in. I've modified the pylint output so that you can see the path to the file that has the problem.

[kattni]

@craigargh @staticmethod is implemented in CircuitPython.

[dhalbert]

Fixed by #166. Thanks @craigargh !