[英]Python Switch/Case Statement Adaptation
好吧,冒着因為沒有“更努力”而被嘲笑的風險,我有一個場景,我一直在嘗試適應 pythonic switch case 語句。 我知道 python 在 3.10 中有新的match
方法,但在我的 AWS 用例中我僅限於 3.8.10。 我一直在閱讀其他語言的 switch case,我想找到一種 pythonic 方法將以下混亂的if/elif/else
語句轉換為干凈的 switch case。 我想知道在這種情況下其他人會做什么
目標:我有一個文件名將被傳遞到這個代碼序列中,我需要返回前三個項目(即transaction_recipient_verification
、 transaction_account_tokenization
等)。 有時代碼會收到一個包含“field_results”或“issuers”的文件名,我需要確保修剪后的返回字符串包含相應的案例。
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}')
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'
以及測試類的代碼:
import random
key = random.choice(sampleKeys)
print(f'before ===> {key}')
a = MainKeyHandleSwitch(key)
trimmed_key = a.get_trimmed_key
print(f'after ===> {trimmed_key}')
我看到你的代碼中有很多重復,所以我首先想到的是:“我可以使用循環來簡化這段代碼嗎?” 答案是肯定的!
由於您的代碼重復使用了六個subjectTypes
並且keySubject
取決於主題類型,因此創建六個類型的列表,然后使用帶有生成器表達式的next()
應該簡化if
的過度豐富(如果沒有任何相關性,字典可以代替)。 此外,您可以使用if-elif-else
子句代替array_data
來防止額外的塊級別。
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}')
如果您正在尋找一種實現 switch 語句的方法,以下是我處理它的方法:
首先為這樣的開關創建一個輔助函數(我將我的放在我在所有項目中使用的“myTools.py”模塊中):
def switch(v): yield lambda *c:v in c
它的工作方式是返回一個捕獲開關值的函數 (lambda),如果該值在其任何參數中,則返回 True。 單個 yield 使 switch() 成為可用於 for 循環的生成器。 for 循環只會執行一次迭代,但鑒於它仍然是一個循環,它將支持 break 語句和最后的 else 子句(當沒有執行任何中斷時)。
這允許以與其他語言(例如 C++)中的 switch 語句非常相似的形式使用一次迭代 for 循環:
value = 5
for case in switch(value): # case is actually a function
if case(0): print("None"); break
if case(2,4,6): print("Even"); break
if case(3,5,7): print("Odd"); break
else:
print("invalid value")
使用這種方法,您可以使您的 switch 函數執行任何類型的模式匹配:
def switchAllIn(v): yield lambda *c:all(s in v for s in c)
此版本的 switch 函數檢查是否所有 case 參數都在 switch 值中:
value = 'The quick brown fox, jumped over the lazy dogs'
for case in switchAllIn(value):
if case('quick','lazy'): print('oxymoron'); break
if case('quick','fast'): print('redundant'); break
else:
print('nothing special')
你甚至可以讓它使用正則表達式:
def switchMatch(v): yield lambda *c:any(re.match(p,v) for p in c)
value = 'The quick brown fox, jumped over the lazy dogs'
for case in switchMatch(value):
if case(r'\bdog\b',r'\bfox\b') and not case('lazy'):
print('lively canine')
break
if case(r'\bquick\b.+\bfox\b'):
print('veloce vulpe')
break
這個解決方案有很大的靈活性。
您實際上不必使用 break,因此您可以通過多個案例,甚至在if case(...):
塊之間執行一些邏輯
您可以將案例與和/或運算符結合起來,例如if case(1) or case(3):
使用中斷時,您可以將for case in switch
中,而不必為case
函數使用不同的名稱
例如:
for case in switch(letter):
if case('a','b'):
for case in switch(number):
if case(1,2,3): print('vitamin'); break
...
break
if case('c','d'):
...
break
例如:
for caseL,caseN in zip(switch(L),switch(N)):
if caseL('a','b') and caseN(1,2,3):
print('vitamin')
break
...
在這種情況下,for 循環將運行多次,您必須使用 continue 而不是 break:
L = [1,2,3,4,5]
for case in map(switch,L):
if case(1,2,3):
print('low')
continue # using continue instead of break
if case(4,5,6):
print('medium')
continue
print('high')
但是,對於您的特定情況,switch 語句不一定是最佳解決方案。 似乎有一種前綴和后綴的組合模式,其間有一組有限的關鍵字。 您可以在由前綴、關鍵字和后綴組成的正則表達式上使用循環來獲取 keySubject:
import re
prefixes = ('transaction_recipient_','transaction_account_')
suffixes = ('_issuers','_field_results','') # in priority order
keywords = r'notification|authentication|verification|tokenization|payment'
for suffix in suffixes:
for prefix in prefixes:
pattern = r'\b('+prefix+keywords+suffix+')\b'
m = re.match(pattern,key)
if not m: continue
keySubject = m.group()
break
else: continue; break
print(f'AFTER ===> {keySubject}')
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