UnboundLocalError:赋值前引用的局部变量“”transaction_id“”

Question

我需要一些帮助来识别这个错误。Python对我来说是新的，所以我每天都在努力学习。

class WithdrawHandler(BaseHandler):
def get(self):
    self.redirect(u"/")

@gen.coroutine
def post(self):
    if not self.current_user:
        self.set_status(403, "Forbidden. Please log in first.")
        return

    withdraw_address = json.loads(self.get_argument("withdrawAddress", None))
    username = tornado.escape.json_decode(self.current_user)
    withdraw_amount_str = json.loads(self.get_argument("withdrawAmount", None))
    withdraw_amount = None
    try:
        withdraw_amount = float(withdraw_amount_str)
    except Exception:
        logging.exception("Withdraw Address: " + withdraw_address + " | Username: " + username + " | Withdraw Amount: " + withdraw_amount_str)
        self.set_status(400, "Invalid amount to withdraw.")
        self.finish()
        return

    if not self.coindaemon.validateaddress(withdraw_address).isvalid:
        logging.info("[Invalid Withdraw Address] Withdraw Address: " + withdraw_address + " | Username: " + username + " | Withdraw Amount: " + withdraw_amount_str)
        self.set_status(400, "Invalid withdraw address. Please enter a valid value.")
        self.finish()
        return        

    if float(self.coindaemon.getbalance(username, minconf=2)) < withdraw_amount:
        logging.info("[Insufficient Funds] Withdraw Address: " + withdraw_address + " | Username: " + username + " | Withdraw Amount: " + withdraw_amount_str)
        self.set_status(400, "Insufficient funds to withdraw.")
        self.finish()
        return

    transaction_time = get_sql_datetime()

    try:
        try:
            self.coindaemon.walletpassphrase(options.walletpassword, 60)
        except bitcoinrpc.exceptions.WalletAlreadyUnlocked:
            pass
        transaction_id = self.coindaemon.sendfrom(username, withdraw_address, withdraw_amount, minconf=2, comment="Withdraw")
        query = 'insert into transactions (transaction_id, transaction_type, transaction_time, username, amount, withdraw_address) values (%s, %s, %s, %s, %s, %s);'
        addtransaction = yield momoko.Op(self.db.execute, query, (transaction_id, "withdraw", transaction_time, username, withdraw_amount, withdraw_address))
        balance = self.coindaemon.getbalance(username, minconf=2)
        self.write(dict(bal=str(balance)))
        self.set_status(200)
    except Exception:
        logging.exception("Transaction ID: " + transaction_id + " | Username: " + username + " | Withdraw Address: " + withdraw_address + " | Withdraw Amount: " + withdraw_amount_str + " | Balance: " + str(balance))
        self.set_status(400, "Error withdrawing.")    
    finally:
        self.finish()

当它被触发时，它会给我一个错误。我一直在搜索，发现了一些关于设置transaction_id全局的东西。这让我很困惑。

Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/tornado/web.py", line 1221, in _when_complete
    if result.result() is not None:
  File "/usr/local/lib/python2.7/dist-packages/tornado/concurrent.py", line 129, in result
    raise_exc_info(self.__exc_info)
  File "/usr/local/lib/python2.7/dist-packages/tornado/gen.py", line 227, in wrapper
    runner.run()
  File "/usr/local/lib/python2.7/dist-packages/tornado/gen.py", line 531, in run
    yielded = self.gen.send(next)
  File "main.py", line 282, in post
    logging.exception("Transaction ID: " + transaction_id + " | Username: " + username + " | Withdraw Address: " + withdraw_address + " | Withdraw Amount: " + withdraw_amount_str + " | Balance: " + str(balance))
UnboundLocalError: local variable 'transaction_id' referenced before assignment

希望外面的大师能帮我领路！

Answer 1

如果self.coindaemon.sendfrom引发异常，则不会设置transaction_id，因此不能将其记录在except子句中。您可以尝试在该行之前将变量设置为默认值。

Answer 2

看起来像是

self.coindaemon.walletpassphrase(options.walletpassword, 60)

因此，在except Exception子句中使用transaction_id之前，决不会设置它。