检查文件一段时间是否可用，然后中断

Question

I've been trying to break a loop which is meant to look for a file in a certain location. My intention is to make my script look for that file for a certain time and then break whether the file is found or not but I can't get any idea.

How can I make the script wait for a certain time and then break when the time is up?

This is my script at this moment:

import os
import time

file_path = r"C:\Users\WCS\Desktop\item.txt"

time_limit = 5
while not os.path.exists(file_path):
    time.sleep(1)
    #is there any logic I can apply here to make the following line valid
    # if waiting_time>=time_limit:break

print("Time's up")

Answer 1

def exists_timeout(path, timeout):
    """Return once <path> exists, or after <timeout> seconds,
    whichever is sooner
    """
    timer = timeout
    while (not os.path.exists(path)) and timer > 0:
        time.sleep(1)
        timer -= 1

Answer 2

Calculate the elapsed time by doing actual time minus start time by using time.time() function and assign a variable ( file_exists in this code) which will be modified and check whether the file exist or not and use it for the loop.

As below:

import os
import time

file_path = r"C:\Users\WCS\Desktop\item.txt"

time_limit = 5

start = time.time()
file_exists = os.path.exists(file_path)

while not file_exists:
    time.sleep(1)
    file_exists = os.path.exists(file_path)
    elapsed = time.time() - start
    if elapsed >= time_limit:
        break
else:
    print("File exist.")

print(elapsed)
print("Time's up")

Answer 3

import os
import time

file_path = r"C:\Users\WCS\Desktop\item.txt"
cTime=0
time_limit = 5

while cTime<time_limit:

    if os.path.exists(file_path)==False:
        cTime=cTime+1
        time.sleep(1)

    else:
        pass

if cTime==5:
    responce="Time's Up"
else:        
    responce='Found'

print(responce)

Answer 4

As roganjosh commented, it would be simpler if you used time stamps. I have added relevant code below:

import os
import time
from datetime import datetime, timedelta

file_path = r"C:\Users\WCS\Desktop\item.txt"
time_limit = datetime.now() + timedelta(seconds=5)
present = datetime.now()   

while (not os.path.exists(path)) and present < time_limit:
    present = datetime.now()
    if present >= time_limit:
        print("Time's up")
        break
    time.sleep(1)

Answer 5

Here's how to do it with the threading.Timer() class. These can be configured to delay a specified amount of time and the call as function of your choosing.

import os
from threading import Timer
import time


file_path = r"C:\Users\WCS\Desktop\item.txt"

# Timer callback function.
def timeout():
    global time_ran_out
    time_ran_out = True

time_limit = 5
time_ran_out = False  # Define variable the callback function modifies.
timer = Timer(time_limit, timeout)  # Create a timer thread object.
timer.start()  # Start the background timer.

while not os.path.exists(file_path):
    time.sleep(1)
    if time_ran_out:
        print('Times up!')
        break

print("Done")

Answer 6

To check for the availability of a file in a certain location you can try the following. The script will break as soon as the file is found otherwise it will wait upto 5 seconds for the file to be available before breaking.

import os
import time

file_path = r"C:\Users\WCS\Desktop\item.txt"

time_to_wait = 5
time_counter = 0
while not os.path.exists(file_path):
    time.sleep(1)
    time_counter += 1
    if time_counter > time_to_wait:break

print("done")