Say what? But why Enum?

Interesting conversation with my colleague friend

A bit of context

I wrote a utility function (as shown below) having a string argument which returns a big message block, depending upon the value of argument.

I thought I wrote some great piece of code,....until I asked my friend to review.

# Code written inside a utility file
def do_something_important(a : str) {
  if a == 'APPLE':
    # A very large dictionary
    message_1 = {....}
    return message_1

  elif a == 'ORANGE':
    # Another very large dictionary
    message_2 = {....}
    return message_2
}

----

# Calling the above function in a separate file
get_message(a='APPLE')

Here’s how our conversation went ahead -

FRIEND: Why don’t you use python enum here?

---

ME: Say what? But why enum?

Enum is a class in python for creating enumerations, which are a set of symbolic names (members) bound to unique, constant values.

---

FRIEND: Well, think of it like this. In future, if some other engineer decides to change the string from APPLE to APPLE_PIE,

• they will have to change in multiple places, where ever this function is called

• or even worse, if they might only change it in the function call, but forgets to update the string in the main function get_message, then your service is doomed to fail.

# Calling with updated string
get_message(a='APPLE_PIE')

---

ME: That is a very unlikely case. Very rare chance of happening.

---

FRIEND: Even if something is very unlikely to happen, it can and will happen. Especially true in software engineering world 😈.
Remember the Murphy’s Law -

“Anything that can go wrong will go wrong”

---

ME: ** Remembering old days of horror… **

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FRIEND: Now, let’s see how things turn out when we use enum in your current code.

utility.py

import enum

# Declare an enum class
class FruitType(enum.Enum):
  APPLE = 'APPLE'
  ORANGE = 'ORANGE'

common.py

from personal_project.service import utils as project_utils

# A dictionary to store messages acc. to enum member
CUSTOM_MESSAGES = {
  project_utils.FruitType.APPLE.value: {....},
  project_utils.FruitType.ORANGE.value: {....}
}

service.py

from personal_project.ui import CUSTOM_MESSAGES
from personal_project.service import utils as project_utils

# Fetch one of the custom message
get_apple_message = CUSTOM_MESSAGES[project_utils.FruitType.APPLE.value]

Let’s analyse -

• Now, if someone wants to change the string value of a fruit type, they will have to go to the enum class FruitType, and just update the value there (only at a single place).

• Also, this refactored code is much more clean and structured.

---

ME: ** Buys coffee for my friend **

THE END