How would I stop a while loop after n amount of time

Question

how would I stop a while loop after 5 minutes if it does not achieve what I want it to achieve   while true      test   0     if test    5          break     test   test - 1   This code throws me in an endless loop

User · Answer

You do not need to use the while True  loop in this case  There is a much simpler way to use the time condition directly   import time    timeout variable can be omitted  if you use specific value in the while condition timeout   300      seconds   timeout start   time time    while time time    lt  timeout start   timeout      test   0     if test    5          break     test -  1

User · Answer

import time  abort after   5   60 start   time time    while True    delta   time time   - start   if delta  gt   abort after      break

User · Answer

Petr Krampl s answer is the best in my opinion  but more needs to be said about the nature of loops and how to optimize the use of the system  Beginners who happen upon this thread may be further confused by the logical and algorithmic errors in the question and existing answers   First  let s look at what your code does as you originally wrote it   while True      test   0     if test    5          break     test   test - 1   If you say while True in a loop context  normally your intention is to stay in the loop forever  If that s not your intention  you should consider other options for the structure of the loop  Petr Krampl showed you a perfectly reasonable way to handle this that s much more clear to someone else who may read your code  In addition  it will be more clear to you several months later should you need to revisit your code to add or fix something  Well-written code is part of your documentation  There are usually multiple ways to do things  but that doesn t make all of the ways equally valid in all contexts  while true is a good example of this especially in this context   Next  we will look at the algorithmic error in your original code  The very first thing you do in the loop is assign 0 to test  The very next thing you do is to check if the value of test is 5  which will never be the case unless you have multiple threads modifying the same memory location  Threading is not in scope for this discussion  but it s worth noting that the code could technically work  but even with multiple threads a lot would be missing  e g  semaphores  Anyway  you will sit in this loop forever regardless of the fact that the sentinel is forcing an infinite loop   The statement test   test - 1 is useless regardless of what it does because the variable is reset at the beginning of the next iteration of the loop  Even if you changed it to be test   5  the loop would still be infinite because the value is reset each time  If you move the initialization statement outside the loop  then it will at least have a chance to exit  What you may have intended was something like this   test   0 while True      test   test - 1     if test    5          break   The order of the statements in the loop depends on the logic of your program  It will work in either order  though  which is the main point   The next issue is the potential and probable logical error of starting at 0  continually subtracting 1  and then comparing with a positive number  Yes  there are occasions where this may actually be what you intend to do as long as you understand the implications  but this is most likely not what you intended  Newer versions of python will not wrap around when you reach the  bottom  of the range of an integer like C and various other languages  It will let you continue to subtract 1 until you ve filled the available memory on your system or at least what s allocated to your process  Look at the following script and the results   test   0  while True      test  -  1      if test   100    0          print  Test    d    test      if test    5          print  Test   5          break   which produces this   Test   -100 Test   -200 Test   -300 Test   -400     Test   -21559000 Test   -21559100 Test   -21559200 Test   -21559300       The value of test will never be 5  so this loop will never exit   To add to Petr Krampl s answer  here s a version that s probably closer to what you actually intended in addition to exiting the loop after a certain period of time   import time  test   0 timeout   300      seconds   timeout start   time time    while time time    lt  timeout start   timeout      if test    5          break     test -  1   It still won t break based on the value of test  but this is a perfectly valid loop with a reasonable initial condition  Further boundary checking could help you to avoid execution of a very long loop for no reason  e g  check if the value of test is less than 5 upon loop entry  which would immediately break the loop     One other thing should be mentioned that no other answer has addressed  Sometimes when you loop like this  you may not want to consume the CPU for the entire allotted time  For example  say you are checking the value of something that changes every second  If you don t introduce some kind of delay  you would use every available CPU cycle allotted to your process  That s fine if it s necessary  but good design will allow a lot of programs to run in parallel on your system without overburdening the available resources  A simple sleep statement will free up the vast majority of the CPU cycles allotted to your process so other programs can do work   The following example isn t very useful  but it does demonstrate the concept  Let s say you want to print something every second  One way to do it would be like this   import time  tCurrent   time time    while True      if time time    gt   tCurrent   1          print  Time    d    time time           tCurrent   time time     The output would be this   Time   1498226796 Time   1498226797 Time   1498226798 Time   1498226799   And the process CPU usage would look like this     That s a huge amount of CPU usage for doing basically no work  This code is much nicer to the rest of the system   import time  tCurrent   time time    while True      time sleep 0 25    sleep for 250 milliseconds     if time time    gt   tCurrent   1          print  Time    d    time time           tCurrent   time time     The output is the same   Time   1498226796 Time   1498226797 Time   1498226798 Time   1498226799   and the CPU usage is way  way lower

User · Answer

I have read this but I just want to ask something  wouldn t something like I have written work at all  I have done the testing for 5 10 and 20 seconds  Its time isn t exactly accurate but they are really close to the actual values   import time  begin time 0 while begin time lt 5       begin time  1     time sleep 1 0  print  The Work is Done

User · Answer

Try this module  http   pypi python org pypi interruptingcow    from interruptingcow import timeout try      with timeout 60 5  exception RuntimeError           while True              test   0             if test    5                  break             test   test - 1 except RuntimeError      pass

User · Answer

Try the following   import time timeout   time time     60 5     5 minutes from now while True      test   0     if test    5 or time time    gt  timeout          break     test   test - 1   You may also want to add a short sleep here so this loop is not hogging CPU  for example time sleep 1  at the beginning or end of the loop body

User · Answer

I want to share the one I am using   import time   provide a waiting-time list  lst    1 2 7 4 5 6 4 3    set the timeout limit timeLimit   4  for i in lst      timeCheck   time time       while True          time sleep i          if time time    lt   timeCheck   timeLimit              print   i  looks ok                break         else              print   i  too long                break   Then you will get    1   looks ok    2   looks ok    7   too long    4   looks ok    5   too long    6   too long    4   looks ok    3   looks ok

[python] How would I stop a while loop after n amount of time?

Examples related to python

Examples related to python-2.7