The only difference here is that this command only works for directories. How can I check whether the Server has database drivers installed? For example, when you copy a large file in Windows, the created file will show its final size throughout the copying process, not its current size. Another alternative is to write it yourself in C or using ctypes - a lot of work. You should also add additional condition on file-size. This can be done by storing a checksum of the initial file, waiting over a predetermined polling period, then comparing the old checksum to the new one. This command will first update pip to the latest version, and then it will list all . Share. Why does Jesus turn to the Father to forgive in Luke 23:34? in code side, the pseudocode similars like below: So, how do i check is a file is already open or is used by other process? @JuliePelletier Can it be done in Perl, without calling a shell command? It really makes sense for Python to grant only certain permissions based what you are planning to do with the file, right? create a game with ps3 style graphics by myself, is it possible? Its syntax is subprocess.check_call(args, *, stdin=None, stdout=None, stderr=None, shell=False) t_0 + n*X + eps it already closed That single character basically tells Python what you are planning to do with the file in your program. File objects have attributes, such as: Could very old employee stock options still be accessible and viable? ex: Move the log files to other place, parse the log's content to generate some log reports. To learn more, see our tips on writing great answers. # retrieve the current position of the pointer, # if the function reaches this statement it means an error occurred within the above context handler, # if the initial size is equal to the final size, the file has most likely. Get started, freeCodeCamp is a donor-supported tax-exempt 501(c)(3) charity organization (United States Federal Tax Identification Number: 82-0779546). Read/Write data. Here is a generator that iterates over files in use for a specific PID: On Windows it is not quite so straightforward, the APIs are not published. For example: I know you might be asking: what type of value is returned by open()? We usually use a relative path, which indicates where the file is located relative to the location of the script (Python file) that is calling the open() function. If favouring the "check whether the legacy application has the file open" (intrusive approach prone to race conditions) then you can solve the said race condition by: Updated NOTE on this solution: Checking with FileAccess.ReadWrite will fail for Read-Only files so the solution has been modified to check with FileAccess.Read. To measure the size of a large file in Python and not suffer any serious performance issues is not as difficult as it may seem, all you really need to do is make use of the file object's read/write pointer. When the body of the context manager has been completed, the file closes automatically. Using access () 3. Tip: You can get the same list with list(f). Not the answer you're looking for? Here's an example. How to do the similar things at Windows platform to list open files. If it encounters an error, it will print the result File is not accessible. Creating an MD5 hash of the entire file before and after a predetermined polling period can tell whether a file has been modified with a high amount of accuracy. Flutter change focus color and icon color but not works. The "a" mode allows you to open a file to append some content to it. Every developer understands the need to create fall back codes, which can save a prorgram from failing in the case that a condition isn't met. So I need a way to check this file is open before the writing process. 1. os.path.exists () As mentioned in an earlier paragraph, we know that we use os.path.exists () to check if a file or directory exists using Python. You could check a file, decide that it is not in use, then just before you open it another process (or thread) leaps in and grabs it (or even deletes it). Looking for connections in the world of IT? But it won't work on Windows as 'lsof' is linux utility. Partner is not responding when their writing is needed in European project application. Context Managers! A file is considered open by a @Ace: Are you talking about Excel? It can actually be done in an OS-independent way given a few assumptions, or as a combination of OS-dependent and OS-independent techniques. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. The only other option I could think of was to try and rename the file or directory containing the file temporarily, then rename it back. That solves the problems brought up in the comments to his answer. Since glob is used for pattern matching, you can use it to check a files status. Python is a relatively easy-to-use language, and it offers a lot of options to the end users. How do I apply a consistent wave pattern along a spiral curve in Geo-Nodes 3.3? Would you check the link of lsof? Weapon damage assessment, or What hell have I unleashed? For checking the existence of a file(s), you can use any of the procedures listed above. I assume that you're writing to the file, then closing it (so the user can open it in Excel), and then, before re-opening it for append/write operations, you want to check that the file isn't still open in Excel? Whether there is a pythonic or non-pythonic way of doing this will probably be the least of your concerns - the hard question will be whether what you are trying to achieve will be possible at all. Unless both the new application and the legacy application need synchronized access for writing to the same file and you are willing to handle the possibility of the legacy application being denied opening of the file, do not use this method. Throw an error when writing to a CSV file if file is in-use in python? You can make a tax-deductible donation here. The technical storage or access that is used exclusively for anonymous statistical purposes. ), checking whether the legacy application has the file open (a la, suspending the legacy application process, repeating the check in step 1 to confirm that the legacy application did not open the file between steps 1 and 2; delay and restart at step 1 if so, otherwise proceed to step 4, doing your business on the file -- ideally simply renaming it for subsequent, independent processing in order to keep the legacy application suspended for a minimal amount of time. Is there any way can do this by using pure python2.4? Each string represents a line to be added to the file. Asking for help, clarification, or responding to other answers. Your email address will not be published. Tip: The write() method returns the number of characters written. First, though, you need to import the subprocess and sys modules into your program: import subprocess import sys result = subprocess.run([sys.executable, "-c", "print ('ocean')"]) If you run this, you will receive output like the following: Output. Due to this, the multiprocessing module allows the programmer to fully leverage multiple processors on a . We further use this method to check if a particular file path refers to an already open descriptor or not. Simply open the file in Python and move the read/write pointer to the end of the file using the seek() method, then retrieve its position using the tell() method, this position is equal to the size of the file in bytes. If Pythons processor is able to locate the file, it will open the file and print the result File is open and available for use. Connect and share knowledge within a single location that is structured and easy to search. PTIJ Should we be afraid of Artificial Intelligence? You can do this with the write() method if you open the file with the "w" mode. I want to open a file which is periodically written to by another application. Here's an example. Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. The '-f' function tests the existence of a file and returns False for a directory. :). Lets use this function to check if any process with chrome substring in name is running or not i.e. So, we will iterate over all the running process and for each process whose name contains the given string,we will keep its info in a list i.e. Tip: The default modes are read ("r") and text ("t"), which means "open for reading text" ("rt"), so you don't need to specify them in open() if you want to use them because they are assigned by default. If you need to create a file "dynamically" using Python, you can do it with the "x" mode. Some familiarity with basic Python syntax. For example copying or deleting a file. Python's os.path.isfile () method can be used to check a directory and if a specific file exists. This is my current working directory: With this mode, you can create a file and then write to it dynamically using methods that you will learn in just a few moments. Here are the Ubuntu sources for lsof. The fstat utility identifies open files. Your choices will be applied to this site only. This code can work, but it can not reach my request, since i don't want to delete the file to check if it is open. Ideally, the code in the print statement can be changed, as per the requirements of your program. See something you don't agree with or feel could be improved? We can do the same in a single line using list comprehension i.e. This will accurately measure any changes made to the file. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. while I vim a file, but it returned False. The system will not allow you to open the file under these circumstances. AntDB database of AsiaInfo passed authoritative test of MIIT. Will your python script desire to open the file for writing or for reading? Is the legacy application opening and closing the file between writes, or does it keep it open? An issue with trying to find out if a file is being used by another process is the possibility of a race condition. sharing (locking): this assumes that the legacy program also opens the file in shared mode (usually the default in Windows apps); moreover, if your application acquires the lock just as the legacy application is attempting the same (race condition), the legacy application will fail. This work is licensed under a Creative Commons Attribution-NonCommercial- ShareAlike 4.0 International License. Context Managers help you work with files and manage them by closing them automatically when a task has been completed. Check if File Exists using the pathlib Module # The pathlib module is available in Python 3.4 and above. source: http://docs.python.org/2.4/lib/bltin-file-objects.html. There are six additional optional arguments. On Windows, you can also directly retrieve the information by leveraging on the NTDLL/KERNEL32 Windows API. There are 10 files in the folder. This is posted as an answer, which it is not. This area of functionality is highly OS-dependent, and the fact that you have no control over the legacy application only makes things harder unfortunately. import psutil for proc in psutil.process_iter (): try: # this returns the list of opened files by the current process flist = proc.open_files () if flist: print (proc.pid,proc.name) for nt in flist: print ("\t",nt.path) # This catches a race condition where a process ends # before we can examine its files except psutil.NoSuchProcess as err: print To use text or binary mode, you would need to add these characters to the main mode. If the user interrupts the program (ctrl-c) after the first rename then the filename will not be restored and the user will be unaware of this condition. Here's a Python decorator that makes using flock easier. I realize it is probably OS dependent, so this may not really be python related right now. En Wed, 07 Mar 2007 02:28:33 -0300, Ros ). Attempt to Write File 3.2. We accomplish this by creating thousands of videos, articles, and interactive coding lessons - all freely available to the public. Our mission: to help people learn to code for free. The test commands only work in Unix based machines and not Windows based OS machines. Sometimes, you may want to delete the content of a file and replace it entirely with new content. This function takes the path to the file as argument and deletes the file automatically. There is a sysinternals tool (handle.exe) that can be used, but I recommend the PyPi module psutil, which is portable (i.e., it runs on Linux as well, and probably on other OS): I like Daniel's answer, but for Windows users, I realized that it's safer and simpler to rename the file to the name it already has. If the connection works Form1 is already open somewhere and I can inform the user about it. 1. By using them, you don't need to remember to close a file at the end of your program and you have access to the file in the particular part of the program that you choose. When you make a purchase using links on our site, we may earn an affiliate commission. I write in Perl. You could use that as the basis of your solution. The value returned is limited to this number of bytes: Important: You need to close a file after the task has been completed to free the resources associated to the file. File objects have their own set of methods that you can use to work with them in your program. Context Managers are Python constructs that will make your life much easier. The test command in the sub-process module is an efficient way of testing the existence of files and directories. 2023 ITCodar.com. Is there a way to check if the current file has been opened by another application? I can still open a file which is opend with 'w+' by another process. If check is true, and the process exits with a non-zero exit code, a CalledProcessError exception will be raised. Awesome, right? None of the other provided examples would work for me when dealing with this specific issue with excel on windows 10. It can actually be done in an OS-independent way given a few assumptions, or as a combination of OS-dependent and OS-independent techniques. To close the file automatically after the task (regardless of whether an exception was raised or not in the try block) you can add the finally block. Notice that we are writing data/ first (the name of the folder followed by a /) and then names.txt (the name of the file with the extension). the try statement is being ignored on my end. The listdir method in Python returns a list of the all files in a specific directory, as specified by the user. Here are multiple ways to check for a specific file or directory using Python. If used it must be a byte sequence, or a string if encoding or errors is specified or text is true. So, we will iterate over all the running process and for each process whose name contains the given string, we will keep it's info in a list i.e. If favouring the "check whether the legacy application has the file open" (intrusive approach prone to race conditions) then you can solve the said race condition by: Unix does not have file locking as a default. If no options are specified, fstat reports on all open files in the system. Can you check for Windows File-type Association, way to check values before Initialisation. The legacy application is opening and closing the file every X minutes, but I do not want to assume that at t = t_0 + n*X + eps it already closed the file. Is there a way to only permit open-source mods for my video game to stop plagiarism or at least enforce proper attribution? attempting to find out what files are open in the legacy application, using the same techniques as ProcessExplorer (the equivalent of *nix's, you are even more vulnerable to race conditions than the OS-independent technique, it is highly unlikely that the legacy application uses locking, but if it is, locking is not a real option unless the legacy application can handle a locked file gracefully (by blocking, not by failing - and if your own application can guarantee that the file will not remain locked, blocking the legacy application for extender periods of time. if both file sizes come back as False, then we can assume the files were in the middle of being written to while attempting to access them, assuming that you have set up your permissions on the file correctly, Measuring a file's size gives us a pretty good idea of whether a file has been modified, but if a file is changed in such as way that it remains the same size after being modified, such as a single character being replaced, then comparing sizes will be ineffective. Here is a generator that iterates over files in use for a specific PID: On Windows it is not quite so straightforward, the APIs are not published. This is the initial file: The lines are added to the end of the file: Now you know how to create, read, and write to a file, but what if you want to do more than one thing in the same program? On Linux it is fairly easy, just iterate through the PIDs in /proc. # if the initial hash is equal to the final hash, the file not changed, # generate a hash if it's a file and add it to the output list, # return False if any files are found to be in use, # generate hashed for all files in a sub-directory, add the output to the list, # if the initial list is equal to the final list, no files in the directory. Let's see some of them. Join Bytes to post your question to a community of 471,987 software developers and data experts. Making statements based on opinion; back them up with references or personal experience. open ("demo.txt") as in Tims example you should use except IOError to not ignore any other problem with your code :). By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The technical storage or access that is used exclusively for statistical purposes. If the file is found, the code will return True, otherwise it'll return False. Browse other questions tagged. Here is how I did it: just write your log processing code in the except part and you are good to go. If favouring the "check whether the legacy application has the file open" (intrusive approach prone to race conditions) then you can solve the said race condition by: checking whether the legacy application has the file open (a la lsof or ProcessExplorer) suspending the legacy application process If we're able to rename it, then no other process is using it. Is there something wrong? Check if File can be Read 2.1. How to work with context managers and why they are useful. I can not include the other thirdparty packages. However, if you're a beginner, there are always ways to learn Python. freeCodeCamp's open source curriculum has helped more than 40,000 people get jobs as developers. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. A slightly more polished version of one of the answers from above. It works well for me on linux, how about windows? Sometimes files are no longer needed. Consider this code: if not-in-use: use-the-file Here's How to Copy a File, want to look for a file in the current directory. os.rename(---); os.rename(---); print "Access ---" You should also catch KeyboardInterrupt and SystemExit exceptions so you can attempt to restore the filename before the application quits. For example: "wb" means writing in binary mode. Simply open the file in Python and move the read/write pointer to the end of the file using the seek () method, then retrieve its position using the tell () method, this position is equal to the size of the file in bytes. You should use the fstat command, you can run it as user : The fstat utility identifies open files. If you try to do so, you will see this error: This particular exception is raised when you try to open or work on a directory instead of a file, so be really careful with the path that you pass as argument. the file. This method follows a symbolic link, which means if the specified path is a symbolic link pointing to a directory, then the method will return True. I'd like to start with this question. Tip: To learn more about exception handling in Python, you may like to read my article: "How to Handle Exceptions in Python: A Detailed Visual Introduction". And have some results: I tried this code, but it doesn't work, no matter i use "r+" or "a+" flag. Learn more about Stack Overflow the company, and our products. Once the full code is compiled and executed, it will close the open file if it was opened. Does Cosmic Background radiation transmit heat? Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. It only takes a minute to sign up. os.path.isdir () method in Python is used to check whether the specified path is an existing directory or not. the legacy application is opening and closing the file every X minutes, but I do not want to assume that at t = t_0 + n*X + eps it already closed the file. Critical issues have been reported with the following SDK versions: com.google.android.gms:play-services-safetynet:17.0.0, Flutter Dart - get localized country name from country code, navigatorState is null when using pushNamed Navigation onGenerateRoutes of GetMaterialPage, Android Sdk manager not found- Flutter doctor error, Flutter Laravel Push Notification without using any third party like(firebase,onesignal..etc), How to change the color of ElevatedButton when entering text in TextField, Pandas dataframe to excel: AttributeError: 'list' object has no attribute 'to_excel', how to set a column to DATE format in xlsxwriter, sheet.nrows has a wrong value - python excel file. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Acceleration without force in rotational motion? To update all Python packages on Linux, you can use the following command in the command line: sudo pip install --upgrade pip && sudo pip freeze --local grep -v '^\-e' cut -d = -f 1 xargs -n1 sudo pip install -U. 1. Join our community and find other helpful and friendly developers, admins, engineers, and other IT people here! The issue with this method is that for larger files it can take quite some time and processing power to calculate a checksum of the file. This did help wait for a file copy transfer to finish, before posting the file.