如果失去互联网连接，如何重置python程序

Question

Ok, so I have this program written in Python and running on Python 2.7 that I use to trade BTC with. I am a complete novice when it comes to programing, but I know enough on how to tweak the bot and create rules for it. It runs fine until there is a change of internet connection ie I trun on/off my VPN. I would like to know what code can I use to restart the program in the event of "Failed to get response"? Your help would be appreciated. Here is the code used to launch the program and the main loop.

def loop_body(self):  
        orders = self.update_portfolio()
        if orders is None:
            return

        if self.get_num_open_bids(orders) + self.get_num_open_asks(orders) >= MAX_OPEN_ORDERS and REMOVE_UNREALISTIC:
            self.update_portfolio

        if self.get_num_open_bids(orders) + self.get_num_open_asks(orders) >= MAX_OPEN_ORDERS:
            if DEBUG_MODE:
                print '---'
                print 'Too many open orders, sleep for', TOO_MANY_OPEN_SLEEP, 'seconds.'
                print " "
                print 'I have', self.get_num_portfolio_bids(), 'open bids,', self.get_num_portfolio_asks(), 'asks.'
                print 'API shows', self.get_num_open_bids(orders), 'open bids,', self.get_num_open_asks(orders), 'asks.'
                print "---"
                print 'Profit :', self.profit, 'CNY'

            sleep(TOO_MANY_OPEN_SLEEP)
            return

        a = None
        b = None
        d = None
        e = None

        market_depth = self.get_market_depth()
        if not market_depth:
            return
        market_lowest_ask = self.get_lowest_market_ask(market_depth)
        a = market_lowest_ask
        market_highest_bid = self.get_highest_market_bid(market_depth)
        d = market_highest_bid
        sleep(5)

        market_depth = self.get_market_depth()
        if not market_depth:
            return
        market_lowest_ask = self.get_lowest_market_ask(market_depth)
        b = market_lowest_ask
        market_highest_bid = self.get_highest_market_bid(market_depth)
        e = market_highest_bid

        if DEBUG_MODE:
            print '---'
            print 'I have', self.get_num_portfolio_bids(), 'open bids,', self.get_num_portfolio_asks(), 'asks.'
            print 'API shows', self.get_num_open_bids(orders), 'open bids,', self.get_num_open_asks(orders), 'asks.'
            print "---"
            print 'Profit :', self.profit, 'CNY'

        my_ask_price_2 = market_lowest_ask - CNY_STEP
        my_bid_price_2 = my_ask_price_2 - MIN_SURPLUS

        if a > b and d > e:
            for trial in xrange(MAX_TRIAL):
                response = self.trader.sell('{0:.2f}'.format(my_ask_price_2), BTC_AMOUNT)
                if response is True:
                    self.portfolio.append(
                        {'bid': my_bid_price_2, 'ask': my_ask_price_2, 'status': 'sell'})
                    if DEBUG_MODE:
                        print "---"
                        print 'I sold', BTC_AMOUNT, 'bitcoins at', my_ask_price_2
                    break
                else:
                    if DEBUG_MODE:
                        print "---"
                        print 'Sell failed:', response
                    break
                break

        my_bid_price = market_highest_bid + CNY_STEP
        my_ask_price = my_bid_price + MIN_SURPLUS 

        if a < b and d < e:
            for trial in xrange(MAX_TRIAL):
                if self.trader.buy('{0:.2f}'.format(my_bid_price), BTC_AMOUNT):
                    self.portfolio.append(
                        {'bid': my_bid_price, 'ask': my_ask_price, 'status': 'buy'})
                    if DEBUG_MODE:
                        print "---"
                        print 'I bought', BTC_AMOUNT, 'bitcoins at', my_bid_price
                    break
                else:
                    if DEBUG_MODE:
                        print "---"
                        print 'Buy failed:', response
                    break
                break

    def start(self):
        self.reset()
        while True:
            self.loop_body()

if __name__ == '__main__':
    bot = Bot()
    bot.start()

Answer 1

It's better to just manage your internet transactions and check to see if requests time out. Then handle the situation appropriately -- sleep, try again, etc.

If you want to restart a python program periodically, you probably need a second script or a shell script, but that's not really the right way to handle this situation.

Answer 2

There's two things you need to do here.

First, presumably that 'event of "Failed to get response"' you're referring to is an exception thrown by whatever that Bot library is. So, you need to handle that exception in some way.

Second, you need a loop-forever while loop wrapped around everything, so after you handle the exception, you go back to the top and try again.

---

If you're on any platform but Windows, and you don't mind ugly exception tracebacks being printed out every time there's a lost connection, this might be easier to do in a wrapper shell script:

#!/bin/sh

while true; do
    python ./myscript.py
done

Whether the program exits normally or quits because of an exception, your shell script will just go through the loop again.

---

If you want to do this in Python, you can change your top-level code to:

if __name__ == '__main__':
    while True:
        try:
            bot = Bot()
            bot.start()
        except Exception as e:
            print('Failed with {!r}, retrying', e)

---

If you actually know the particular exception you're getting—if it wasn't in your original tracebacks, it'll be the type of e in the new loop—you may want to handle just that exception. That way, if there's something else wrong with your program, instead of looping forever, it'll show you what went wrong. (There's nothing worse than a typo causing an infinite loop of Failed with NameError: 'slef' messages…) Once you know it, just change the except line to:

except LostConnectionException as e: