How can I make a python script change itself?

Question

How can I make a python script change itself?

To boil it down, I would like to have a python script (run.py)like this

a = 0
b = 1
print          


        

Answer 1

Make a file a.txt that contains one character on one line:

0

Then in your script, open that file and retrieve the value, then immediately change it:

with open('a.txt') as f:
    a = int(f.read())
with open('a.txt', 'w') as output:
    output.write(str(a+1))
b = 1
print a+b

On the first run of the program, a will be 0, and it will change the file to contain a 1. On subsequent runs, a will continue to be incremented by 1 each time.