Using a keystroke to repeat a function

Question

I have a backup script that simply runs every day and backs up files to a directory if they exist in source dir but not in destination dir.

Sometimes (rarely) the script will fall over if a file isn't permissioned properly.

I've got around this using a try/except block.

However what I want to do now is to display the error message from the except block and then to say

>>> Press Enter to re-run backup

and then for the script to re-run the copying process which is a defined function.

So to summarise:

Script runs
Script throws error
User follows instructions from error message
User presses "Enter" key to re-run the copying function

I am running windows if that makes a difference (when I was googling this problem a lot of the results were to do with python on windows)

possible duplicate of [Python read a single character from the user](http://stackoverflow.com/questions/510357/python-read-a-single-character-from-the-user) — ivan_pozdeev, Sep 09 '14 at 11:24
Not a duplicate. The keystroke isn't the main part of my question. Moreso the recognition of that keystroke to re-run a function once an error message is shown.Although people reading this question might find that question useful as well, so thank you. — Joe Smart, Sep 09 '14 at 12:22

Roberto Reale · Accepted Answer · 2014-09-09T08:59:12.133

1

You can use raw_input() (or simply input() if using Python 3) to wait for Enter and a condition variable to control looping through the copying process until successful.

from sys import stderr

def run_backup():
    print "running backup"
    raise  # this simulates an error


backup_completed = False

while not backup_completed:
    try:
        run_backup()
        backup_completed = True
    except:
        print >> stderr, "Error message..."
        raw_input(">>> Press Enter to re-run backup")

edited Sep 09 '14 at 08:59

answered Sep 09 '14 at 08:42

Roberto Reale

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Will this re-run the script though. I think I understand what you've written in terms of the error etc. but on the enter keystroke does this repeat `run_backup` – Joe Smart Sep 09 '14 at 08:46
It will call again `run_backup()`. Is this not the expected behaviour? – Roberto Reale Sep 09 '14 at 08:48
That's exactly what I wanted. I'm just a bit new to python and still learning some stuff so wasn't 100% sure it'd do this. – Joe Smart Sep 09 '14 at 08:57
That's great :) As you can see, the `raise` in the `run_backup()` function is just there to simulate an error condition. Also, an this answer be correct, please accept it, so that it may be useful for others as well. – Roberto Reale Sep 09 '14 at 09:01

score 0 · Answer 2 · answered Sep 09 '14 at 08:40

Seems pretty simple to me. You can just use raw_input to make the script wait an Enter key-press:

while True:
    try:
        # run the script
    except SomeException as e:
        # print the error message and recovery instructions

        raw_input('Press Enter to re-run backup.')

Using a keystroke to repeat a function

2 Answers2