Development guidelines

Python guidelines are documented on python website under the name PEP8. For Python, we use all PEP8 conventions excepted that we allow 120 characters per line instead of 80.


Many editor or IDE (Integrated Development Environments) integrate tools to check or fix coding guidelines. For example:

  • Eclipse with pydev extension
  • pyCharm
  • Spyder
  • Vim (with plugin)
  • Emacs (with plugin)

If your editor do not support natively PEP8, you can search if a plugin exists or use these two external tools:

  • flake8 : check coding guidelines
  • autopep8 : fix automatically guidelines

These tools may be available in your system package manager (apt-get, urpmi, ports, ...) or can be install using pip or easy_install.

To run autopep8:

autopep8 -i -a --max-line-length=119 --ignore E26,E265


Don't mix tab and spaces. For new project, use only spaces.


Add a Doctring for all classes and functions.


Modules or packages

Module names are the same as the file name. Modules should have short, lowercase names, without underscore. Singular is better than plural.

# Yes:
import tree

# No:
import Tree

For C/C++/Fortran extension modules embedded in a Python package that provide a more Pythonic interface, the C/C++/Fortran module has a leading underscore (e.g. _amlpymodule).

Class Names

Class names use the CapsWords convention.

class Tree:

Class Methods and Function Names

Class methods and function names should be lowercase, with words separated by underscores.

def this_is_a_function():

class ClassName:
    def class_method(self):

Exception Names

class VertexError(TypeError):

Whitespace in Expressions and Statements

Avoid extraneous whitespace in the following situations:

Immediately inside parentheses, brackets or braces.

# Yes:
spam(ham[1], {eggs: 2})

# No:
spam( ham[ 1 ], { eggs: 2 } )

Immediately before a comma, semicolon, or colon:

# Yes:
if x == 4:
    print x, y
    x, y = y, x

# No:
if x == 4 :
    print x , y
    x , y = y , x

Immediately before the open parenthesis that starts the argument list of a function call:

# Yes:
# No:
spam (1)

Immediately before the open parenthesis that starts an indexing or slicing:

# Yes:
dict['key'] = list[index]
# No:
dict ['key'] = list [index]

Use spaces around arithmetic operators:

# Yes:

i = i + 1
submitted += 1
x = x * 2 - 1
hypot2 = x * x + y * y
c = (a + b) * (a - b)

# No:

submitted +=1
x = x*2 - 1
hypot2 = x*x + y*y
c = (a+b) * (a-b)

Don't use spaces around the '=' sign when used to indicate a keyword argument or a default parameter value.


def complex(real, imag=0.0):
    return magic(r=real, i=imag)


def complex(real, imag = 0.0):
    return magic(r = real, i = imag)


Use property instead of get, set methods. Hide get and set methods with a leading underscore. Classes with properties have to inherit from object.

# Ok, new style

class Tree(object):
    def root(self):
        return self._root

    def root(self, root):
        self._root = root

# Ok, old style

class Tree(object):
    def _get_root(self):
        return self._root
    def _set_root(self, _root):
        self._root = _root
    root = property(_get_root, _set_root)

# No:
class Tree(object):
    def get_root(self):
        return self._root
    def set_root(self, _root):
        self._root = _root
    root = property(get_root,set_root)



Plugin classes (factories):

mypackage/plugins/groupnames/ contains class PluginAbc.

For example:

oalab/plugins/applets/ (class HelpWidget)

If your package defines a new group of plugin, just add a "" module to describe it (documentation, interfaces, ...)


For example:

oalab/plugin/ (contains IPluginApplet)

C++ specific Coding Guidelines

General Practices

  • Write warning free code. What generates a warning on one platform will generate errors on another.
  • Don't use NULL for pointers. Use 0 instead.
  • Don't compare == 'true' or 'false'. Use (x) or (!x) instead.
  • Don't put an else right after a return.
  • Use Doxygen markup language in any new class header files.
  • Forward declare classes in your header files instead of including them whenever possible.
  • Use smart pointers instead of raw pointers.

Code Layout


Use 4 spaces per indentation level. Do not use tabs.



int fct( int i, int j )
    // ...


for( int i= 1; i <= n; ++i )
    // ...

while( cond )
    // ...


while( cond );