How to check whether a file is empty or not

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

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

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

There is a race condition because the file may be removed between the calls to os.path.isfile(fpath) and os.path.getsize(fpath), in which case the proposed function will still raise an exception

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

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

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

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

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 (e.g. 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.

Better way to test size of compressed files: read it directly using the appropriate compression module. You would only need to read the first line of the file, for example.

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

An easy simple method I used recently is this:

f = open('test.txt', 'w+')

f.seek(0) #Unecessary but important if file was manipulated before reading
if f.read() == '':
    print("no data found")
else:
    print("Data present in file")

You can use the above as inspiration for your desired uses (keeping in mind I am pretty new to file handling this seemed to suit my desired use in a program I was writing).

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()

There is a simpler way not using the os library:

with open('filename') as myfile:
    if len(myfile.readlines()):
        print("It's not empty")