Correct way to check for empty or missing file in Python

Question

I want to check both whether a file exists and, if it does, if it is empty.

If the file doesn't exist, I want to exit the program with an error message.

If the file is empty I want to exit with a different error message.

Otherwise I want to continue.

I've been reading about using Try: Except: but I'm not sure how to structure the code 'Pythonically' to achieve what I'm after?

Thank you for all your responses, I went with the following code:

try:
    if os.stat(URLFilePath + URLFile).st_size > 0:
        print "Processing..."
    else:
        print "Empty URL file ... exiting"
        sys.exit()
except OSError:
    print "URL file missing ... exiting"
    sys.exit()

Just to clarify, the program is loading URLs from the file I'm checking, doing stuff with them, then zeroing out the file using open(URLFile, 'w').close(). I'm going to run the program every few minutes so I want it to exit if no new URLs have been added in the meantime. — TheRogueWolf
– TheRogueWolf, Commented Jul 19, 2013 at 13:55
Using exceptions for foreseeable and avoidable errors is lazy. Check if the file exists, and if it does, then check its size. — Richard Haven
– Richard Haven, Commented Jun 11, 2016 at 1:00

TheRogueWolf · Accepted Answer · 2013-07-19 14:19:16Z

18

I'd use os.stat here:

try:
    if os.stat(filename).st_size > 0:
       print "All good"
    else:
       print "empty file"
except OSError:
    print "No file"

edited Jul 19, 2013 at 14:19

TheRogueWolf

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answered Jul 19, 2013 at 13:42

mgilson

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4 Comments

Markus Unterwaditzer Over a year ago

This is IMO the best solution.

psukys Over a year ago

what about zero byte files?

mgilson Over a year ago

@shookees -- Forgive my ignorance, but how is a zero byte file different from an empty file?

mgilson Over a year ago

@TheRogueWolf -- Thanks for catching that. Too early to code apparently :)

Tim Pietzcker · Accepted Answer · 2013-07-19 13:37:47Z

2

How about this:

try:
    myfile = open(filename)
except IOError:  # FileNotFoundError in Python 3
    print "File not found: {}".format(filename)
    sys.exit()

contents = myfile.read()
myfile.close()

if not contents:
    print "File is empty!"
    sys.exit()

edited Jul 19, 2013 at 13:37

answered Jul 19, 2013 at 13:32

Tim Pietzcker

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3 Comments

mgilson Over a year ago

Is FileNotFoundError a thing? (it isn't for me with python2.7 -- That just raises a NameError) For me it's an IOError. Also, I would discourage reading the entire file (what if the user accidentally provides a file which is 8 Gb?) I think you can get the empty/non-empty info from os.stat.

Tim Pietzcker Over a year ago

@mgilson: Right; I tested open("blargh") in Python 3 and had expected the exception also to be present in Python 2. So my previous version was actually correct :)

mgilson Over a year ago

Nice, I hadn't realized that they subclassed IOError and created FileNotFoundError in py3k. cool.

Jakob Bowyer · Accepted Answer · 2013-07-19 13:37:55Z

1

os.path.exists and other functions in os.path.

As for reading,

you want something like

if not os.path.exists(path):
    with open(path) as fi:
        if not fi.read(3):  #avoid reading entire file.
             print "File is empty"

edited Jul 19, 2013 at 13:37

answered Jul 19, 2013 at 13:30

Jakob Bowyer

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1 Comment

Sepehr GH Over a year ago

I suppose you meant if os.path.exists(path):, otherwise this code is trying to open a file that does not exist.

Roland Smith · Accepted Answer · 2013-07-19 13:41:42Z

0

Try this:

import os
import sys

try:
    s = os.stat(filename)
    if s.st_size == 0:
        print "The file {} is empty".format(filename)
        sys.exit(1)
except OSError as e:
    print e
    sys.exit(2)

answered Jul 19, 2013 at 13:41

Roland Smith

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Comments

NiktW · Accepted Answer · 2022-10-07 16:00:59Z

0

Try this:

if file.tell() == 0:
    print("File is empty!")
else: print("File is not empty")

answered Oct 7, 2022 at 16:00

NiktW

1

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