How to check whether a file is empty or not

Question

I have a text file. How can I check whether it's empty or not?

Answer 1

>>> import os
>>> os.stat("file").st_size == 0
True

Answer 2

import os    
os.path.getsize(fullpathhere) > 0

Answer 3

Both getsize() and stat() will throw an exception if the file does not exist. This function will return True/False without throwing (simpler but less robust):

import os
def is_non_zero_file(fpath):  
    return os.path.isfile(fpath) and os.path.getsize(fpath) > 0

Answer 4

If for some reason you already had the file open, you could try this:

>>> with open('New Text Document.txt') as my_file:
...     # I already have file open at this point.. now what?
...     my_file.seek(0) # Ensure you're at the start of the file..
...     first_char = my_file.read(1) # Get the first character
...     if not first_char:
...         print "file is empty" # The first character is the empty string..
...     else:
...         my_file.seek(0) # The first character wasn't empty. Return to the start of the file.
...         # Use file now
...
file is empty

Answer 5

If you are using Python 3 with pathlib you can access os.stat() information using the Path.stat() method, which has the attribute st_size (file size in bytes):

>>> from pathlib import Path
>>> mypath = Path("path/to/my/file")
>>> mypath.stat().st_size == 0 # True if empty

Answer 6

Combining ghostdog74's answer and the comments:

>>> import os
>>> os.stat('c:/pagefile.sys').st_size==0
False

False means a non-empty file.

So let's write a function:

import os

def file_is_empty(path):
    return os.stat(path).st_size==0

Answer 7

if you have the file object, then

>>> import os
>>> with open('new_file.txt') as my_file:
...     my_file.seek(0, os.SEEK_END) # go to end of file
...     if my_file.tell(): # if current position is truish (i.e != 0)
...         my_file.seek(0) # rewind the file for later use 
...     else:
...         print "file is empty"
... 
file is empty

Answer 8

Since you have not defined what an empty file is: Some might also consider a file with just blank lines as an empty file. So if you want to check if your file contains only blank lines (any white space character, '\\r', '\\n', '\\t') , you can follow the example below:

Python 3

import re

def whitespace_only(file):
    content = open(file, 'r').read()
    if re.search(r'^\s*$', content):
        return True

Explanation: the example above uses a regular expression (regex) to match the content ( content ) of the file.

Specifically: for a regex of: ^\\s*$ as a whole means if the file contains only blank lines and/or blank spaces.

• ^ asserts position at start of a line
• \\s matches any white space character (equal to [\\r\\n\\t\\f\\v ])
• * Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
• $ asserts position at the end of a line

Answer 9

If you want to check if a CSV file is empty or not, try this:

with open('file.csv', 'a', newline='') as f:
    csv_writer = DictWriter(f, fieldnames = ['user_name', 'user_age', 'user_email', 'user_gender', 'user_type', 'user_check'])
    if os.stat('file.csv').st_size > 0:
        pass
    else:
        csv_writer.writeheader()

Answer 10

An important gotcha: a compressed empty file will appear to be non-zero when tested with getsize() or stat() functions:

$ python
>>> import os
>>> os.path.getsize('empty-file.txt.gz')
35
>>> os.stat("empty-file.txt.gz").st_size == 0
False

$ gzip -cd empty-file.txt.gz | wc
0 0 0

So you should check whether the file to be tested is compressed (eg examine the filename suffix) and if so, either bail or uncompress it to a temporary location, test the uncompressed file, and then delete it when done.

Answer 11

A Complete Example For Appending JSON To A File

Reusable Function

import json
import os 

def append_json_to_file(filename, new_data):
    """ If filename does not exist """
    data = []
    if not os.path.isfile(filename):
        data.append(new_data)
        with open(filename, 'w') as f:
            f.write(json.dumps(data))
    else:
        """ If filename exists but empty """
        if os.stat(filename).st_size == 0:
            data = []
            with open(filename, 'w') as f:
                f.write(json.dumps(data))
        """ If filename exists """
        with open(filename, 'r+') as f:
            file_data = json.load(f)
            file_data.append(new_data)
            f.seek(0)
            json.dump(file_data, f)

Run It

filename = './exceptions.json'
append_json_to_file(filename, {
    'name': 'LVA',
    'age': 22
})
append_json_to_file(filename, {
    'name': 'CSD',
    'age': 20
})        

Result

[{"name": "LVA", "age": 22}, {"name": "CSD", "age": 20}]