Storage Classes

Storage classes are used to store a structured or multi-component data record. By using a storage class, the individual data components can be referenced by name instead of using a tuple or list structure and referencing the components by index. A data field name provides a more meaningful indicator of the type of data and its purpose as compared to a simple integer index value.

Naming

The name of a storage class should follow the rules for naming classes:

The name should be descriptive of the data actually stored in instances of the storage class.
StudentRecord ListNode GridCell MatrixElement MapElement
The name should consist of more than one word and typically ends with one of the following nouns:
Record Element Cell Node Item
Do not name a storage class Storage or Record.

Storage classes must be commented with a description and an indication of their visibility.

Constructor

A storage class should only include a constructor that either takes no arguments

class StudentRecord:
def __init__( self ): # Do this.
self.idNum = 0
self.firstName = None
self.lastName = None
self.gpa = 0.0

or arguments comprised of all or a subset of the data fields defined by the class

class StudentRecord:
def __init__( self, idNum, firstName, lastName ): # Or do this.
self.idNum = idNum
self.firstName = firstName
self.lastName = lastName
self.gpa = 0.0

No processing or executable statements other than assignments should be performed within the constructor of a storage class. For example, the following should not be done

class StudentRecord:
def __init__( self, line ): # Don't do this.
lineParts = line.split()
self.idNum = int(lineParts[0])
self.firstName = lineParts[1]
self.lastName = lineParts[2]
self.gpa = 0.0

Data Attributes

The data fields or attributes of a storage class should:

have meaningful names as related to the data they store,
be public since they are directly accessed by the code that uses them.