Update 'PYGUIDE.md'

PYGUIDE.md

@@ -18,5 +18,79 @@ For code analysis, we enforce the usage of [pylint](https://www.pylint.org/) wit
 * Name your folders and files in lowercase.
 * Your class names must start in capital letters and follow the python CapWords pattern. 
 * Methods and properties that return lists must end in "s".
+* Methods and variables should be lowercase and use _ (underscore) as word separator.
 * Constants names must be all capitals.
-* Avoid the usage of "get_" and "set_" methods whenever possible, by using @property and @variable.setter decorators instead.
+* Avoid the usage of "get_" and "set_" methods whenever possible, by using @property and @variable.setter decorators instead.
+* "Private" methods, variables and properties start with _ (underscore)
+
+## Imports
+
+All the imports should be defined at the top of the file after the license and contact information comment
+
+```python
+"""
+MyClass module
+SPDX - License - Identifier: LGPL - 3.0 - or -later
+Copyright © 2020 Project Author name name@concordia.ca
+"""
+
+import sys
+```
+
+Ensure that your imports are used and remove any unused.
+
+
+## Object attributes and methods
+
+Use properties whenever possible and encapsulate the access to all the calculated object attributes into a properties as shown in the following example.
+
+```python
+
+  @property
+  def object_attribute(self):
+    if self._object_attribute is None:
+      self._object_attribute = ...
+      ...
+    return self._object_attribute        
+
+```
+
+or if the property can be modified like in the following example
+
+```python
+
+  @property
+  def object_changeable_attribute(self):    
+    return self._object_changeable_attribute       
+    
+  @object_changeable_attribute.setter
+  def object_changeable_attribute(self, value):
+    self._object_changeable_attribute = value
+
+```
+
+If your method or attribute returns a complex object use type hints as in this example
+
+```python
+
+  @property
+  def complex_object(self) -> ComplexObject:    
+    return self._object_changeable_attribute       
+    
+  def new_complex_object(self, first_param, second_param) -> ComplexObject:
+    return ComplexObject(first_param, second_param, self.property)
+
+```
+
+always access your variable throught the method and avoid to access directly.
+
+```python
+
+  @property
+  def object_attribute(self):    
+    return self._object_attribute       
+    
+  def operation(self, first_param, second_param):
+    return self.object_attribute * 2
+
+```