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

For an example (changing the value of a each time its run):

a = 0
b = 1
print a + b

with open(__file__, 'r') as f:
    lines = f.read().split('\n')
    val = int(lines[0].split(' = ')[-1])
    new_line = 'a = {}'.format(val+1)
    new_file = '\n'.join([new_line] + lines[1:])

with open(__file__, 'w') as f:
    f.write('\n'.join([new_line] + lines[1:]))