Python retries opening the file

What is the best practice to try to open a file and try again after n seconds?

Currently, I do this:

import os
from os import path
import shutil

dir_path = path.abspath(path.join("foo", "bar"))
destination_path = path.abspath(path.join("foo", "dest_dir"))

for f in dir_path:
    try:
        # try to open the file if the file isn't used any longer
        file_opened = open(f, 'r')
        # move the file on successful opening
        shutil.move(file_opened, destination_path)
        file_opened.close()
    except IOError:
        return False

So, at the moment I don’t handle exceptions. I consider creating extra functions to open the file and call the function on excepth using time.sleep(n).

I’m sure there is something else, though….

I won’t use it

with open(f, 'rb') as file_opened: 
    do whatever` 

Edit:

A process creates a file, and I want the Python process to move the file after determining that the file is written/created. So, I added shutil.move in the above code to show the whole case.

Edit:

Please find the code I developed to solve the problem below. I ended up writing my own custom solution to handle it:

import os
from os import path
import psutil
from retry import retry
import shutil
from subprocess import check_output,Popen, PIPE
import glob
import time

class FileHandler:
    def __init__(self, fn_source, dir_source):
        self.file_source_name = fn_source
        self.file_source_path = path.join(dir_source, self.file_source_name)
        self.dir_dest_path = path.join(dir_source, "test")
        self.file_dest_path = path.join(self.dir_dest_path, self.file_source_name)

def check_file(self):
        if os.path.exists(self.file_source_path):
            try:
                os.rename(self.file_source_path, self.file_source_path)
                print("file renamed")
                return True
            except:
                print("can not rename the file.. retrying")
                time.sleep(1)
                self.check_file()
        else:
            print("source file does not exist... retrying")
            time.sleep(5)
            self.check_file()

def check_destination(self):
        if os.path.exists(self.file_source_path) and not os.path.exists(self.file_dest_path):
            return True
        elif os.path.exists(self.file_source_path) and os.path.exists(self.file_dest_path):
            try:
                print(self.file_dest_path, self.file_source_name)
                os.remove(self.file_dest_path)
                return True
            except Exception as e:
                print("can not remove the file.. retrying")
                time.sleep(5)
                self.check_destination()

def move_file(self):
        if self.check_destination():
            print(self.file_source_path)
            shutil.move(self.file_source_path, self.file_dest_path)
            print("moved", str(self.file_source_path))
            return True
        else:
            print("can not move the file.. retrying")
            time.sleep(1)
            self.move_file()

def file_ops(self):
        if self.check_file():
            self.move_file()
        else:
            print("source does not exist")
            time.sleep(1)
            self.file_ops()
        return True

def each_file_ops(fn, dir_source):
    fh = FileHandler(fn, dir_source)
    return fh.file_ops()

def main(dir_source):
    dir_files = glob.glob(path.join(dir_source, '*.txt'))
    if dir_files:
        [each_file_ops(f, dir_source) for f in dir_files]
    else:
        print("source dir is empty")
        time.sleep(1)
        main(dir_source)

if __name__ == '__main__':
    main(path.join(""))

You can use the retry module for such retries. This makes the code look clearer. pip install retry The module should be installed

from retry import retry
import shutil

@retry((FileNotFoundError, IOError), delay=1, backoff=2, max_delay=10, tries=100)
def attempt_to_move_file(fname, dest_path):
    # Your attempt to move file
    # shutil.move(fname, destination_path)

Using the above code, when attempt_to_move_file is called, whenever we encounter FileNotFoundError or IOError, it will retry (up to 100 attempts) > and the retry occurs at sleep 1, 2, 4, 8, 10, 10, 10 … Seconds between attempts