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I'm trying to open a file, and if the file doesn't exist, I need to create it and open it for writing. I have this so far:

#open file for reading
fn = input("Enter file to open: ")
fh = open(fn,'r')
# if file does not exist, create it
if (!fh) 
fh = open ( fh, "w")

The error message says there's an issue on the line if(!fh). Can I use exist like in Perl?

If you don't need atomicity you can use os module:

import os

if not os.path.exists('/tmp/test'):
    os.mknod('/tmp/test')

UPDATE:

As Cory Klein mentioned, on Mac OS for using os.mknod() you need a root permissions, so if you are Mac OS user, you may use open() instead of os.mknod()

import os

if not os.path.exists('/tmp/test'):
    with open('/tmp/test', 'w'): pass

open() in Python does not create a file if it doesn't exist, You should use open with the w+ mode: file = open('myfile.dat', 'w+'). will not create the file if it does not exist. When fstream is constructed with std::ios::in included, if the file does not exist, the std::ios::in portion fails because the file does not exist. In more details: after calling open() to open the file because std::ios::in is in the mode, fail() will evaluate to true.

'''
w  write mode
r  read mode
a  append mode

w+  create file if it doesn't exist and open it in (over)write mode
    [it overwrites the file if it already exists]
r+  open an existing file in read+write mode
a+  create file if it doesn't exist and open it in append mode
'''

example:

file_name = 'my_file.txt'
f = open(file_name, 'a+')  # open file in append mode
f.write('python rules')
f.close()

I hope this helps. [FYI am using python version 3.6.2]

Shell script to create a file if it doesn't exist?, Possibly simpler solution, no need to do explicit tests, just use: mkdir -p /Scripts touch /Scripts/file.txt. If you don't want the "modification" time of an existing file.txt � Create a File If Not Exists via PowerShell June 8, 2015 by Morgan We can check if a file exist or not by using the PowerShell cmdlet Test-Path and create new file using New-Item cmdlet. The below powershell script will check whether the file sample.txt is already exists or not under the path C:Share.

Well, first of all, in Python there is no ! operator, that'd be not. But open would not fail silently either - it would throw an exception. And the blocks need to be indented properly - Python uses whitespace to indicate block containment.

Thus we get:

fn = input('Enter file name: ')
try:
    file = open(fn, 'r')
except IOError:
    file = open(fn, 'w')

Python Create File (Empty Text File), You will learn basic of creating file and functions with examples.you can w write mode (if the file doesn't exist create it and open it in write� If you create a web based application, the better solution is to check the directory exists or not then create the file if not exist. If exists, recreate again. private File createFile(String path, String fileName) throws IOException { ClassLoader classLoader = getClass().getClassLoader(); File file = new File(classLoader.getResource(".").getFile() + path + fileName); // Lets create the directory try { file.getParentFile().mkdir(); } catch (Exception err) { System.out.println("ERROR

Using input() implies Python 3, recent Python 3 versions have made the IOError exception deprecated (it is now an alias for OSError). So assuming you are using Python 3.3 or later:

fn = input('Enter file name: ')
try:
    file = open(fn, 'r')
except FileNotFoundError:
    file = open(fn, 'w')

Create a file if it doesn't exist, You can use the below-mentioned code to create a file if it does not exit:- import os. if not os.path.exists('/tmp/test'):. os.mknod('/tmp/test'). If the file DOES exist you are making a directory (but not doing anything to create the file). You also don't need the null operation, you should be able to simply do: #! /bin/bash - if [[ ! -e /Scripts/file.txt ]]; then mkdir -p /Scripts touch /Scripts/file.txt fi [command2]

I think this should work:

#open file for reading
fn = input("Enter file to open: ")
try:
    fh = open(fn,'r')
except:
# if file does not exist, create it
    fh = open(fn,'w')

Also, you incorrectly wrote fh = open ( fh, "w") when the file you wanted open was fn

Inject : create file if it doesn't exist � Issue #115 � jondot/hygen � GitHub, Hi! Thanks for the amazing Project! Problem statement : Is there any way we can create a file if it doesn't exist while injection. Went through the� //If you want to force the file to be empty then you want to use the 'w' flag: var fd = fs.openSync(filepath, 'w'); //That will truncate the file if it exists and create it if it doesn't. //Wrap it in an fs.closeSync call if you don't need the file descriptor it returns.

PHP: Create file if it doesn't already exist., In this tutorial, we will use PHP to check if a file exists before we attempt to create it. Using a Write mode “w” or “w+” will create a file if not exists in Python. Or use this code first check file exists or not, then do create it.

fopen can create or append a file, Use fopen to create a file if it doesn't exist and to append to a file if it does exist. When creating an object of File you have to pass the name of the file with extension (with path if required). createNewFile () if-else statement will return a boolean result- true and false, where true means file created and false means failed to create a file. For that will show a message and check condition in the.

How to create a file in Java if one doesn't exists, The File.createNewFile() method creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist. This methods� If the specified file does not exist, it is created; if it does exist and it is not read-only, the contents are overwritten. By default, full read/write access to new files is granted to all users. The file is opened with read/write access and must be closed before it can be opened by another application.

Comments
  • Possible duplicate of Open in Python does not create a file if it doesn't exist
  • macOS requires sudo privileges to run mknod so this is unlikely to be portable to Mac unless you're running your python script with sudo.
  • This creates a race condition between exists() and open().
  • r+ does not create any file. As also mentioned here and here(in the description) r+ is for opening a file in reading and writing mode. Correct it as it might confuse people :)
  • w+ also clears the content of the file. Here's a complete (longer) description of each mode.
  • It does not work on Windows: Exception has occurred: FileNotFoundError
  • I have been trying to figure out why this is preferable to open(fn, 'a').close(). Is it because the implicit seek in append may be too expensive?
  • You are assuming that the file cannot be opened because it does not exist. It could be that you don't have read permissions, or the filename is invalid in some way. Bare except is not a good idea.
  • I understand that, (now) but this will be effective enough for his level of programming, it's not like we are teaching him the etiquette of programming or prepping him for class though.
  • OK, the poor guy comes from Perl so he needs all the help he can get.
  • This made my day. We could explain the intricacies, but, I want to sleep, maybe I will explain pathing in the morning to him, or do you want to?
  • You don't need to write a dissertation on effective exception handling, just give him good examples. There are other answers which do that.
  • There's a typo in the code. It should be with open('file.txt', 'w+') as f:.
  • @Flux fixed typo