Python Switch/Case Statement Adaptation

Ok, at the risk of being ridiculed for not ‘trying harder’, I have a scenario that I’ve been attempting to adapt to a pythonic switch case statement. I know python has the new match method in 3.10 but I’m limited to 3.8.10 in my AWS use case. I’ve been reading up on switch cases in other languages and I want to find a pythonic way to convert the following jumbled mess of if/elif/else statements to a clean switch case. I am wondering what others would do in this scenario

OBJECTIVE: I have a filename that will be passed into this sequence of code and I need to return the first three items (i.e. transaction_recipient_verification, transaction_account_tokenization, etc). Occasionally the code will receive a filename containing “field_results” or “issuers” and I need to make sure that the trimmed return string contains the respective case.

import random

sampleKeys = [
    'transaction_recipient_notification_status_sent/transaction_recipient_notification_status_sent_2021_10_29_12_02_14.snappy',
    'transaction_recipient_payment_status_success/transaction_recipient_payment_status_success_2021_10_29_12_02_14.snappy',
    'transaction_recipient_verification_rvdm_failure/transaction_recipient_verification_rvdm_failure_2021_10_29_12_02_14.snappy',
    'transaction_recipient_verification_rvdm_failure_field_results/transaction_recipient_verification_rvdm_failure_2021_10_29_12_02_14.snappy',
    'transaction_recipient_authentication_status_success/transaction_recipient_authentication_status_success_2021_10_29_12_02_14.snappy',
    'transaction_recipient_authentication_status_success_field_results/transaction_recipient_authentication_status_success_2021_10_29_12_02_14.snappy',
    'transaction_account_tokenization_success/transaction_account_tokenization_success_2021_10_29_12_02_14.snappy',
    'transaction_account_tokenization_success_issuers/transaction_account_tokenization_success_2021_10_29_12_02_14.snappy',
    'transaction_recipient_payment_status_terminated/transaction_recipient_payment_status_terminated_2021_10_29_12_02_14.snappy',
    'transaction_recipient_verification_rvdm_success/transaction_recipient_verification_rvdm_success_2021_10_29_12_02_14.snappy',
    'transaction_recipient_verification_rvdm_success_field_results/transaction_recipient_verification_rvdm_success_2021_10_29_12_02_14.snappy',
    'transaction_recipient_notification_status_received/transaction_recipient_notification_status_received_2021_10_29_12_02_14.snappy',
    'transaction_recipient_authentication_status_success/transaction_recipient_authentication_status_success_2021_10_29_11_17_45.snappy'
    
]

key = random.choice(sampleKeys)

array_data = any(substring in key for substring in ['_issuers', '_field_results'])
if not array_data:
    if 'transaction_recipient_notification' in key:
        keySubject = 'transaction_recipient_notification'
    elif 'transaction_recipient_authentication' in key:
        keySubject = 'transaction_recipient_authentication'
    elif 'transaction_recipient_verification' in key:
        keySubject = 'transaction_recipient_verification'
    elif 'transaction_account_verification' in key:
        keySubject = 'transaction_account_verification'
    elif 'transaction_account_tokenization' in key:
        keySubject = 'transaction_account_tokenization'
    elif 'transaction_recipient_payment' in key:
        keySubject = 'transaction_recipient_payment'
else:
    if '_issuers' in key:
        if 'transaction_recipient_notification' in key:
            keySubject = 'transaction_recipient_notification_issuers'
        elif 'transaction_recipient_authentication' in key:
            keySubject = 'transaction_recipient_authentication_issuers'
        elif 'transaction_recipient_verification' in key:
            keySubject = 'transaction_recipient_verification_issuers'
        elif 'transaction_account_verification' in key:
            keySubject = 'transaction_account_verification_issuers'
        elif 'transaction_account_tokenization' in key:
            keySubject = 'transaction_account_tokenization_issuers'
        elif 'transaction_recipient_payment' in key:
            keySubject = 'transaction_recipient_payment_issuers'
    elif '_field_results' in key:
        if 'transaction_recipient_notification' in key:
            keySubject = 'transaction_recipient_notification_field_results'
        elif 'transaction_recipient_authentication' in key:
            keySubject = 'transaction_recipient_authentication_field_results'
        elif 'transaction_recipient_verification' in key:
            keySubject = 'transaction_recipient_verification_field_results'
        elif 'transaction_account_verification' in key:
            keySubject = 'transaction_account_verification_field_results'
        elif 'transaction_account_tokenization' in key:
            keySubject = 'transaction_account_tokenization_field_results'
        elif 'transaction_recipient_payment' in key:
            keySubject = 'transaction_recipient_payment_field_results'
print(f'BEFORE ===> {key}')
print(f'AFTER  ===> {keySubject}')

Possible Direction:

import re
    
class MainKeyHandleSwitch:
    
    ARRAY_OPTIONS = ['_issuers', '_field_results']
        
    def __init__(self,key):
        self._original_key = key
        self._array_data = any(substring in key for substring in self.ARRAY_OPTIONS)
        self._trimmed_dict = self.trimmed_dict()
    
    @property
    def get_trimmed_dict(self):
        return self._trimmed_dict
    
    @property
    def get_trimmed_key(self):
        return self.__get_key_subject__()
    
    def trimmed_dict(self):
        trim_dict = dict()
        trim_dict['case_one'] = re.search('transaction_recipient_notification+', self._original_key)
        trim_dict['case_two'] = re.search('transaction_recipient_authentication+', self._original_key)
        trim_dict['case_three'] = re.search('transaction_recipient_verification+', self._original_key)
        trim_dict['case_four'] = re.search('transaction_account_verification+', self._original_key)
        trim_dict['case_five'] = re.search('transaction_account_tokenization+', self._original_key)
        trim_dict['case_six'] = re.search('transaction_recipient_payment+', self._original_key)
        return trim_dict
    
    def __get_key_subject__(self):
        obj = next(item for item in list(self._trimmed_dict.values()) if item is not None)
        if not self._array_data:
            return obj.group(0)
        else:
            if '_issuers' in self._original_key:
                return f'{obj.group(0)}_issuers'
            
            elif '_field_results' in self._original_key:
                return f'{obj.group(0)}_field_results'        

And the code to test the class:

import random

key = random.choice(sampleKeys)
print(f'before ===> {key}')
a = MainKeyHandleSwitch(key)
trimmed_key = a.get_trimmed_key
print(f'after  ===> {trimmed_key}')

Answer

I see a lot of repetition in your code, so the first thing I’ll think of would be: “can I use a loop to simply this code?” and the answer is yes!

Since your code repeatedly used the six subjectTypes and the keySubject depends on the subject type, creating a list of the six types then use next() with a generator expression should simplify the over abundance of if‘s (If there weren’t any correlations, a dictionary would work instead). Also, instead of array_data, you can use an if-elif-else clause to prevent an extra block level.

sampleKeys = [...]
key = random.choice(sampleKeys)

subjectTypes = ['transaction_recipient_notification', 'transaction_recipient_authentication',
                'transaction_recipient_verification', 'transaction_account_verification',
                'transaction_account_tokenization', 'transaction_recipient_payment']

if '_issuers' in key:
    keySubject = next(t + '_issuers' for t in subjectTypes if t in key)
elif '_field_results' in key:
    keySubject = next(t + '_field_results' for t in subjectTypes if t in key)
else:
    keySubject = next(t for t in subjectTypes if t in key)

print(f'BEFORE ===> {key}')
print(f'AFTER  ===> {keySubject}')