How to save the file with different name and not overwriting existing one

Question

I need to run a python script repeatedly over different data set. This python script test.py processes the data set, plot and save the result using the command.

plt.savefig('result.png')

How can I ensure that when the same test.py scripts runs on another data set.. the new result.png doesn't overwrite my previous result? Basically before executing plt.savefig('result.png'), I need to check if result.png already exist and if does then rename the result to any other name like

result1.png
result2.png

Otherwise, in the next post processing the file is overwritten.

Answer 1

You can use os.path.exists to check whether the file already exists, and if so, append a number. Repeat with the new file name until you find one that does not yet exist.

def unique_file(basename, ext):
    actualname = "%s.%s" % (basename, ext)
    c = itertools.count()
    while os.path.exists(actualname):
        actualname = "%s (%d).%s" % (basename, next(c), ext)
    return actualname

Example-usage:

for i in range(5):
    with open(unique_file("foo", "txt"), "w") as f:
        f.write(str(i))

Answer 2

import time
if os.path.exists('result.png'):
    plt.savefig('result_{}.png'.format(int(time.time())))
else:
    plt.savefig('result.png')