Using typedef C like enum in python

Question

I am a long-time C developer who is starting to use Python (more specifically 3.7.12) in some applications.

I am wondering if I can use something similar to the typedef enum structure that we have in C. My point is: It is very useful when we create a variable that can only assume some values and the IDE provide hints to those possible values, like the following example:

typedef enum{
   NO_ERROR_PC          = 0,        
   ERROR_ERROR_PC       = 1,        
   ERROR_CMD_NOT_KNOWN  = 2,
   ...
}PC_COM_ERROR_T;

PC_COM_ERROR_T          f_error;

switch(f_error){
   //... compiler checks if there is anything missing, 
   //or if a case for a value that is not defined has been created...
}

void newFuction(PC_COM_ERROR_T error){
    //makes very clear what values are accepted, provide hints and compiler checks
}

This is also very useful when we need to assign a value to f_error because the IDE already provide hints.

I have been wonder around, but I did not find anything that would perform as well as I need.

It does part of the job indeed. Do you have any more specific advice regarding the Enum module? — Felipe Schneider
– Felipe Schneider, Commented Jan 13, 2022 at 11:27
Since, I am not versed in C, I can't give you anything else. If you can be specific about what you are trying to do with it, maybe I can help. — itprorh66
– itprorh66, Commented Jan 13, 2022 at 14:03
To be more specific, I would like to have something that would limit the scope of possible inputs of a variable or identify, during coding, that one variable is been assignment to a value that is not listed in the Enum. — Felipe Schneider
– Felipe Schneider, Commented Jan 13, 2022 at 18:41
Unlike in C Python does not have strong typing, thus you can never limit the type of data assigned to a variable either during coding or during execution Python does offer type hinting, which helps define the scope of data types a variable can handle within the function signature, but this is not enforced during execution. — itprorh66
– itprorh66, Commented Jan 13, 2022 at 19:03

Dharman · Accepted Answer · 2022-01-20 19:48:50Z

1

Welcome to Python, and thanks for asking a great question! I think you may want to try type hints. Most IDE's use them to provide very useful hints and linting.

Your code should approximately translate as:

from enum import IntEnum

class PC_COM_ERROR_T(IntEnum):
    NO_ERROR_PC = 0
    ERROR_ERROR_PC = 1
    ERROR_CMD_NOT_KNOWN = 2

f_error = PC_COM_ERROR_T.ERROR_ERROR_PC

def newFuction(error: PC_COM_ERROR_T):
    # Uncomment the line below you absolutely want to have strong typing.
    # assert isinstance(error, PC_COM_ERROR_T) 
    print(error.value)


newFuction(f_error)

As @itprorh66 wrote above, Python does not have strong typing. Coming from C, I understand that you miss the structure it provides. If you find a place where you absolutely have to have strong typing, you can insert assert isinstance(error, PC_COM_ERROR_T) as a function precondition, but I almost never see it being used.

edited Jan 20, 2022 at 19:48

Dharman♦

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answered Jan 20, 2022 at 19:43

user23952

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2 Comments

Felipe Schneider Over a year ago

Thank you for the time and especially for the the isinstance line!

user23952 Over a year ago

You are most welcome, @FelipeSchneider!

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