Restart thread after exception on Python

Question

I wrote this script in order to extract metadata from data on specific ftp then save it on specific directory and waits a random time and extract again etc... So there is 2 points : First : to extract from specific ftp Second : to save it and wait a random time which depends of the ftp used.

Sometime I have timeout issue from ftp. When it occurs there is no extract, save or waiting from the thread anymore. The others thread continue to work until they meet a timeout issue too.

I tried to catch exception in order to "restart" the thread which concerns by the ftp timeout issue. But nothing changes.

Someone please can help me to find a way to "restart" the thread?

Many thank's

class ftp_id(Thread):
    def __init__(self, ftpID):
        Thread.__init__(self)
        self.ftpID = ftpID
    def run(self):
        while True:
            with verrou:
                siteID = self.ftpID
                directory = str(datetime.now())[:-16].replace('-', '')
                filename = siteID + '_' + str(datetime.now())[:-7].replace(':', '').replace(' ', '_').replace('-', '') + '.txt'
                dictstr = myExtract(siteID)
                myWriteFile(directory, filename, dictstr)
                pendingtime = myWaiting(siteID, dictstr)
            time.sleep(pendingtime)
        except :
            self.stop = True
            self.stop = False
            self.start()
            self.join()

thread_01 = ftp_id("ftp-01")
thread_02 = ftp_id("ftp-02")
thread_03 = ftp_id("ftp-03")
thread_04 = ftp_id("ftp-04")

thread_01.start()
thread_02.start()
thread_03.start()
thread_04.start()

thread_01.join()
thread_02.join()
thread_03.join()
thread_04.join()

Answer 1

Threads cannot be restarted. So you should put the exception handling inside the while-block, and never exit the loop:

def download(server):
    while True:
        try:
            with verrou:
                now = datetime.now()
                directory = '{:%Y%m%d}'.format(now)
                filename = '{}_{:%Y%m%d_%H%M%S}.txt'.format(server, now)
                dictstr = myExtract(server)
                myWriteFile(directory, filename, dictstr)
                pendingtime = myWaiting(server, dictstr)
            time.sleep(pendingtime)
        except:
            # restart
            pass

threads = [
    Thread(target=download, args=(server,))
    for server in ["ftp-01", "ftp-02", "ftp-03", "ftp-04"
]

for thread in threads:
    thread.start()

for thread in threads:
    thread.join()

Answer 2

threads cannot be restarted in python ... of coarse you could just implement your own "thread" class thats not really a thread

class ftp_id(object): # this is a bad name for a class please see pep8
    def __init__(self, ftpID):
        super(ftp_id,self)
        self.ftpID = ftpID
        self.thread = None
        self.thread_stop = False
    def __getattr__(self):
        return getattr(self.thread)
    def start(self):
        if self.thread:
           self.thread_stop = True
           self.thread.terminate()
           self.thread.join()

        self.thread = threading.Thread(target = self.run)
        self.thread.start()
    def run(self):
        self.thread_stop = False
        while not self.thread_stop:
            with verrou:
                siteID = self.ftpID
                directory = str(datetime.now())[:-16].replace('-', '')
                filename = siteID + '_' + str(datetime.now())[:-7].replace(':', '').replace(' ', '_').replace('-', '') + '.txt'
                dictstr = myExtract(siteID)
                myWriteFile(directory, filename, dictstr)
                pendingtime = myWaiting(siteID, dictstr)
            time.sleep(pendingtime)

although i dont know if this actually answers your question