How do I check whether a file exists without exceptions?

If the reason you're checking is so you can do something like if file_exists: open_it(), it's safer to use a try around the attempt to open it. Checking and then opening risks the file being deleted or moved or something between when you check and when you try to open it.

If you're not planning to open the file immediately, you can use os.path.isfile

Return True if path is an existing regular file. This follows symbolic links, so both islink() and isfile() can be true for the same path.

import os.path
os.path.isfile(fname) 

if you need to be sure it's a file.

Starting with Python 3.4, the pathlib module offers an object-oriented approach (backported to pathlib2 in Python 2.7):

from pathlib import Path

my_file = Path("/path/to/file")
if my_file.is_file():
    # file exists

To check a directory, do:

if my_file.is_dir():
    # directory exists

To check whether a Path object exists independently of whether is it a file or directory, use exists():

if my_file.exists():
    # path exists

You can also use resolve(strict=True) in a try block:

try:
    my_abs_path = my_file.resolve(strict=True)
except FileNotFoundError:
    # doesn't exist
else:
    # exists

Use os.path.exists to check both files and directories:

import os.path
os.path.exists(file_path)

Use os.path.isfile to check only files (note: follows symlinks):

os.path.isfile(file_path)

Unlike isfile(), exists() will return True for directories. So depending on if you want only plain files or also directories, you'll use isfile() or exists(). Here is some simple REPL output:

>>> os.path.isfile("/etc/password.txt")
True
>>> os.path.isfile("/etc")
False
>>> os.path.isfile("/does/not/exist")
False
>>> os.path.exists("/etc/password.txt")
True
>>> os.path.exists("/etc")
True
>>> os.path.exists("/does/not/exist")
False

import os

if os.path.isfile(filepath):
   print("File exists")

import os
os.path.exists(path) # Returns whether the path (directory or file) exists or not
os.path.isfile(path) # Returns whether the file exists or not

Testing for files and folders with os.path.isfile(), os.path.isdir() and os.path.exists()

Assuming that the "path" is a valid path, this table shows what is returned by each function for files and folders:

You can also test if a file is a certain type of file using os.path.splitext() to get the extension (if you don't already know it)

>>> import os
>>> path = "path to a word document"
>>> os.path.isfile(path)
True
>>> os.path.splitext(path)[1] == ".docx" # test if the extension is .docx
True

TL;DR
answer is: use the pathlib module

Pathlib is probably the most modern and convenient way for almost all of the file operations. For the existence of a file or a folder a single line of code is enough. If file is not exists, it will NOT throw any exception.

from pathlib import Path

if Path("myfile.txt").exists(): # works for both file and folders
    # do your cool stuff...

The pathlib module was introduced in Python 3.4, so you need to have Python 3.4+, this lib makes your life much easier while working with files and folders and it is pretty to use, here is more doc about it (https://docs.python.org/3/library/pathlib.html).

BTW, if you are going to reuse the path, then it is better to assign it to a variable

so will become

from pathlib import Path

p = Path("loc/of/myfile.txt")
if p.exists(): # works for both file and folders
    # do stuffs...
#reuse 'p' if needed.

You could try this (safer):

try:
    # http://effbot.org/zone/python-with-statement.htm
    # 'with' is safer to open a file
    with open('whatever.txt') as fh:
        # Do something with 'fh'
except IOError as e:
    print("({})".format(e))

The ouput would be:

([Errno 2] No such file or directory: 'whatever.txt')

Then, depending on the result, your program can just keep running from there or you can code to stop it if you want.

Additionally, os.access():

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()

Being R_OK, W_OK, and X_OK the flags to test for permissions (doc).

exists() and is_file() methods of 'Path' object can be used for checking if a given path exists and is a file.

Python 3 program to check if a file exists:

# File name:  check-if-file-exists.py

from pathlib import Path

filePath = Path(input("Enter path of the file to be found: "))

if filePath.exists() and filePath.is_file():
    print("Success: File exists")
else:
    print("Error: File does not exist")

Output:

$ python3 check-if-file-exists.py

Enter path of the file to be found: /Users/macuser1/stack-overflow/index.html

Success: File exists

$ python3 check-if-file-exists.py

Enter path of the file to be found: hghjg jghj

Error: File does not exist

Use os.path.exists() to check whether file exists or not:

def fileAtLocation(filename,path):
    return os.path.exists(path + filename)
 

filename="dummy.txt"
path = "/home/ie/SachinSaga/scripts/subscription_unit_reader_file/"


if fileAtLocation(filename,path):
   print('file found at location..')
else:
   print('file not found at location..')

import os

# for testing purpose args defaulted to current folder & file. 
# returns True if file found
def file_exists(FOLDER_PATH='../', FILE_NAME=__file__):
    return os.path.isdir(FOLDER_PATH) \
        and os.path.isfile(os.path.join(FOLDER_PATH, FILE_NAME))

Basically a folder check, then a file check with proper directory separator using os.path.join.

Another possible option is to check whether the filename is in the directory using os.listdir()

import os
if 'foo.txt' in os.listdir():
    # Do things

this will return true if it is and false if not

This is how i found a list of files(in this images) in one folder and searched it in a folder (with subfolders)

# This script concatenates javascript files into a unified js to reduce server round-trips

import os
import string
import math
import ntpath
import sys

#import pyodbc

import gzip
import shutil

import hashlib

# BUF_SIZE is totally arbitrary, change for your app!
BUF_SIZE = 65536  # lets read stuff in 64kb chunks

# Iterate over all js files in the folder and combine them
filenames = []
shortfilenames = []

imgfilenames = []
imgshortfilenames = []

#Get a unified path so we can stop dancing with user paths
# Determine where files are on this machine (%TEMP% dir and app installation dir)
if '.exe' in sys.argv[0]: # if getattr(sys, 'frozen', False):
    RootPath = os.path.abspath(os.path.join(__file__, "..\\"))
   

elif __file__:
    RootPath = os.path.abspath(os.path.join(__file__, "..\\"))
 
print ("\n storage of image files RootPath: %s\n" %RootPath)


FolderPath = "D:\\TFS-FARM1\\StoneSoup_STS\\SDLC\\Build\\Code\\StoneSoup_Refactor\\StoneSoupUI\\Images"
print ("\n storage of image files in folder to search: %s\n" %FolderPath)


for root, directories, filenames2 in os.walk(FolderPath):
    for filename in filenames2:
        fullname = os.path.join(root, filename)        
        filenames.append(fullname)
        shortfilenames.append(filename)        

for i, fname in enumerate(shortfilenames):        
        print("%s - %s" % (i+1, fname))

for root, directories, filenames2 in os.walk(RootPath):
    for filename in filenames2:
        fullname = os.path.join(root, filename)        
        imgfilenames.append(fullname)
        imgshortfilenames.append(filename)        

for i, fname in enumerate(imgshortfilenames):        
        print("%s - %s" % (i+1, fname))
        
for i, fname in enumerate(imgshortfilenames):
        if fname in shortfilenames:
            print("%s - %s exists" % (i+1, fname))
        else:
            print("%s - %s ABSENT" % (i+1, fname))