Using the @property + setter encapsulation, I need a class that raises an exception when someone tries to change the account_number. However, in the __init__ function, I need to set the value. This is the code, it generates recursion.
class SingleBankAccount:
def __init__(self, account_number, account_balance):
self.account_number = account_number
self.account_balance = account_balance
@property
def account_number(self):
return self.account_number
@account_number.setter
def account_number(self, number):
# if there is a number already, raise exception, otherwise set it
if self.account_number:
raise AccountException("Someone tried to change the account number!")
else:
self.account_number = number
This is the error:
File "main.py", line 17, in account_number
if self.account_number:
File "main.py", line 13, in account_number
return self.account_number
File "main.py", line 13, in account_number
return self.account_number
File "main.py", line 13, in account_number
return self.account_number
[Previous line repeated 993 more times]
RecursionError: maximum recursion depth exceeded
Plz help me understand why.
>Solution :
You are setting the self.account_number property within the setter. The proper pythonic way is to use a "private" property:
class SingleBankAccount:
def __init__(self, account_number, account_balance):
self.account_number = account_number
self.account_balance = account_balance
@property
def account_number(self):
return self._account_number
@account_number.setter
def account_number(self, number):
# if there is a number already, raise exception, otherwise set it
if hasattr(self, "_account_number"):
raise AccountException("Someone tried to change the account number!")
else:
self._account_number = number
hasattr is to avoid issues with the property not being set.