If you’ve had experience programming in languages such as C++ or Java, you are probably familiar with enums (enumerations), utilised to create name constants. These are particularly useful when you have a variable that is expected to take one of a predefined set of values, e.g., days of the week or student grades. While Python does not have an explicit enum data type, Python’s standard library contains an enum module that allows you to create enumerations.
Enums are basically collections of related constants, each with a meaningful name assigned to it. The use of enums in programming is beneficial because they make code more legible, maintainable, and type-safe. They replace magic numbers or strings with meaningful labels which make code more self-explanatory. Enums are easy to define and manage, enhancing code maintainability.
To create an enumeration in Python, import the Enum class from the enum module, define a new class (e.g., TaskStatus) that inherits from Enum. Then define each member with a unique name and optional value. For instance:
from enum import Enum
class TaskStatus(Enum):
TODO = 0
IN_PROGRESS = 1
DONE = 2
ABANDONED = -1
You can check all enum members by casting it into a list or access each member either by using their names or by their value.
Python allows seamless iteration over and comparison of related constants. You can use len() function to count the number of enum members and iterate over enums the same way as with any Python iterable. For example:
num_statuses = len(TaskStatus)
print(num_statuses)
for status in TaskStatus:
print(status.name, status.value)
Ordering in Enums can be achieved through the auto() helper function. If the enum has ‘n’ members, values are assigned 1 to n. If passed a start value, say k, auto(k) will start enumeration from k and go up to k + n.
The real benefit of enums is that they allow for creating more practical code. The tutorial uses a program that allows tasks to transition between different states – “To-Do”, “In-Progress”, “Done”, and “Abandoned”. The status updates are managed using an update_status() method that checks if each transition is valid. If a transition isn’t valid, it raises a ValueError exception.
In conclusion, this tutorial demonstrates that enums are an incredibly useful feature in Python for their ease of use and implementation, benefits towards code legibility, and flexibility for more practical applications.