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Contributing to mGear

Argument shorthands

In Maya, some arguments have a short equivalent. Don't use it.

Wrong

pm.workspace(q=True, rd=True)

Right

pm.workspace(query=True, rootDirectory=True)

The reason is readability. The second reason is that these shorthands are provided not to make your code shorter, but to reduce the filesize of Maya's own internal scene format, the .ma files. It's not Pythonic, it's an optimisation.


Members & __init__

Always declare all members of a class in the __init__ method.

Wrong

class MyClass(object):
    def __init__(self):
        super(MyClass, self).__init__()

        self.height = 5

    def resize(self, width, height):
        self.height = height
        self.width = width

Right

class MyClass(object):
    def __init__(self):
        super(MyClass, self).__init__()

        self.height = 5
        self.width = 5

    def resize(self, width, height):
        self.height = height
        self.width = width

The reason is discoverability. When members are attached to self in any subsequent method, it becomes difficult to tell whether it is being created, or modified. More importantly, it becomes impossible to tell which member is used externally.

from mymodule import MyClass

myclass = MyClass()
myclass.width = 5
print(myclass.other_member)

And at that point, impossible to maintain backwards compatibility should any of the methods creating new members be removed or refactored.


Relative imports

Where possible, relatively reference the root mgear package.

Wrong

from mgear.core import rigbits

Right

from .maya import rigbits

This enables mgear to be bundled together with another library, e.g. from .vendor.mgear import maya and also avoids mgear being picked up from another location on a user's machine and PYTHONPATH. It also shortens the import line, which is always nice.


Avoid import as

Where possible, avoid the use of import ... as ....

from mgear.core import rigbits as rb

This makes it more difficult to understand where a particular call is coming from, when read by someone who didn't initially make that import.

swg.run_important_function()
# What does this do? :O

Tuple versus List

Use List when mutability is required or intended, tuple otherwise.

for item in ("good", "use", "of", "tuple"):
    pass

Tuples will tell you and the user when used them in an unintended way.

# You
immutable = (1, 2, 3)

# User
immutable.append(4)
# ERROR

Whereas a list would not, and cause a difficult-to-debug error. The fabled "Works on my machine (tm)".


Mutable arguments

Never use a mutable object in an argument signature.

def function(wrong=[]):
    wrong.append(1)
    print(wrong)


function()
# [1]
function()
# [1, 1]
function()
# [1, 1, 1]

The same goes for {}. Instead, pass None and convert internally.

def function(wrong=None):
    wrong = wrong or []
    wrong.append(1)
    print(wrong)

function()
# [1]
function()
# [1]
function()
# [1]

Docstrings

All docstrings are written in Google Napoleon format.

def function(a, b=True):
    """Summary here, no line breaks

    Long description here.

    Arguments:
        a (str): A first argument, mandatory
        b (bool, optional): A second argument

    Example:
        >>> print("A doctest")
        'A doctest'

    """

Quotation Marks

Default to double-ticks, fallback to single-tick.

# Right
side = "Right"

# Wrong
side = 'Left'

# Right
def function():
    """It's a single tick"""

# Wrong
def function():
    '''It's a single tick"""

Code Style

We are refactoring all the code to PEP8 If you want to contribute please follow the PEP8 standard


Ignore PEP8 Errors

"W503": Break bfore or after binary operator

Line break for long arguments

# No
function(arg1, arg2,
         kwarg=False, kwarg2=True)

# No
function(
    arg1, arg2,
    kwarg=False, kwarg2=True)

# Yes
function(arg1,
         arg2,
         kwarg=False,
         kwarg2=True)
# Yes
function(
    arg1, arg2, kwarg=False, kwarg2=True)

# OK
function(
    arg1,
    arg2,
    kwarg=False,
    kwarg2=True)