Python linux file exists

Pythonic way to check if a file exists? [duplicate]

Actual duplicate question: Safely create a file if and only if it does not exist with python. In Python 3.3+, use the ‘x’ flag when open() ing a file to avoid race conditions.

5 Answers 5

To check if a path is an existing file:

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.

Of course, you can get into a race condition where the file doesn’t exist when you check, but springs into existence before you can create it. Extremely unlikely, but possible.

This will return true if a directory exists by the given name, in which case a subsequent creation of the file will fail.

I think you are thinking of os.path.exists, which returns True if the path exists (i.e. is a file or a directory). As shown above, os.path.isfile returns True when the path is a regular file.

This answer is outdated. On Python 3.4+ use pathlib , like this: Path(«path/to/file»).is_file() if you want to check that it’s a file and that it exists or Path(«path/to/file»).exists() if you only want to know that it exists (but might be a directory).

Instead of os.path.isfile , suggested by others, I suggest using os.path.exists , which checks for anything with that name, not just whether it is a regular file.

if not os.path.exists(filename): file(filename, 'w').close() 

The latter will create the file if it exists, but not otherwise. It will, however, fail if the file exists, but you don’t have permission to write to it. That’s why I prefer the first solution.

For Python 3 need to replace file with open : if not os.path.exists(filename): open(filename, «w+»).close()

It seems to me that all other answers here (so far) fail to address the race-condition that occurs with their proposed solutions.

Any code where you first check for the files existence, and then, a few lines later in your program, you create it, runs the risk of the file being created while you weren’t looking and causing you problems (or you causing the owner of «that other file» problems).

If you want to avoid this sort of thing, I would suggest something like the following (untested):

import os def open_if_not_exists(filename): try: fd = os.open(filename, os.O_CREAT | os.O_EXCL | os.O_WRONLY) except OSError, e: if e.errno == 17: print e return None else: raise else: return os.fdopen(fd, 'w') 

This should open your file for writing if it doesn’t exist already, and return a file-object. If it does exists, it will print «Ooops» and return None (untested, and based solely on reading the python documentation, so might not be 100% correct).

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How to Check if a File Exists in Python with isFile() and exists()

Dionysia Lemonaki

When working with files in Python, there may be times when you need to check whether a file exists or not.

But why should you check if a file exists in the first place?

Confirming the existence of a specific file comes in handy when you want to perform particular operations, such as opening, reading from, or writing to that file.

If you attempt to perform any of the operations mentioned above and the file doesn’t exist, you will come across bugs and your program will end up crashing.

So, to perform operations and prevent your program from crashing, it is a helpful first step to check if a file exists on a given path.

Thankfully, Python has multiple built-in ways of checking whether a file exists, like the built-in os.path and pathlib modules.

Specifically, when using the os.path module, you have access to:

• the os.path.isfile(path) method that returns True if the path is a file or a symlink to a file.
• the os.path.exists(path) method that returns True if the path is a file, directory, or a symlink to a file.

And when using the pathlib module, you have access to the pathlib.Path(path).is_file() function, which returns True if path is a file and it exists.

In this article, you will learn how to use Python to check if a file exists using the os.path and pathlib modules.

How to Check if a File Exists Using the os.path Module

The os module is part of the standard library (also known as stdlib ) in Python and provides a way of accessing and interacting with the operating system.

With the os module, you can use functionalities that depend on the underlying operating system, such as creating and deleting files and folders, as well as copying and moving contents of folders, to name a few.

Since it is part of the standard library, the os module comes pre-packaged when you install Python on your local system. You only need to import it at the top of your Python file using the import statement:

The os.path is a submodule of the os module.

It provides two methods for manipulating files — specifically the isfile() and exists() methods that output either True or False , depending on whether a file exists or not.

Since you will be using the os.path submodule, you will instead need to import that at the top of your file, like so:

How to Check if a File Exists Using the os.path.isfile() Method in Python

The general syntax for the isfile() method looks like this:

The method accepts only one argument, path , which represents the defined path to the file whose existence you want to confirm.

The path argument is a string enclosed in quotation marks.

The return value of the isfile() method is either a Boolean value — either True or False depending on whether that file exists.

Keep in mind that if the path ends in a directory name and not a file, it will return False .

Let’s see an example of the method in action.

I want to check whether an example.txt file exists in my current working directory, python_project .

The example.txt is on the same level as my Python file main.py , so I am using a relative file path.

I store the path to example.txt in a variable named path .

Then I use the isfile() method and pass path as an argument to check whether example.txt exists in that path.

Since the file does exist, the return value is True :

import os.path path = './example.txt' check_file = os.path.isfile(path) print(check_file) # output # True 

Ok, but what about absolute paths?

Here is the equivalent code when using an absolute path. The example.txt file is inside a python_project directory, which is inside my home directory, /Users/dionysialemonaki/ :

import os.path path = '/Users/dionysialemonaki/python_project/example.txt' print(os.path.isfile(file_path)) # Output # True 

And as mentioned earlier, the isfile() method only works for files and not directories:

import os.path path = '/Users/dionysialemonaki/python_project' check_file = os.path.isfile(path) print(check_file) # output # False 

If your path ends in a directory, the return value is False .

How to Check if a File Exists Using the os.path.exists() Method in Python

The general syntax for the exists() method looks like this:

As you can see from the syntax above, the exists() method looks similar to the isfile() method.

The os.path.exists() method checks to see whether the specified path exists.

The main difference between exists() and isfile() is that exists() will return True if the given path to a folder or a file exists, whereas isfile() returns True only if the given path is a path to a file and not a folder.

Keep in mind that if you don’t have access and permissions to the directory, exists() will return False even if the path exists.

Let’s go back to the example from the previous section and check whether the example.txt file exists in the current working directory using the exists() method:

import os.path path = './example.txt' check_file = os.path.exists(path) print(check_file) # output # True 

Since the path to example.txt exists, the output is True .

As mentioned earlier, the exists() method checks to see if the path to a directory is valid.

In the previous section, when I used the isfile() method and the path pointed to a directory, the output was False even though that directory existed.

When using the exists() method, if the path to a directory exists, the output will be True :

import os.path path = '/Users/dionysialemonaki/python_project' check_file = os.path.exists(path) print(check_file) # output # True 

The exists() method comes in handy when you want to check whether a file or directory exists.

How to Check if a File Exists Using the pathlib Module

Python 3.4 version introduced the pathlib module.

Using the pathlib module to check whether a file exists or not is an object-oriented approach to working with filesystem paths.

Like the os.path module from earlier on, you need to import the pathlib module.

Specifically, you need to import the Path class from the pathlib module like so:

Then, create a new instance of the Path class and initialize it with the file path you want to check:

from pathlib import Path # create a Path object with the path to the file path = Path('./example.txt') 

You can use the type() function to check the data type:

from pathlib import Path path = Path('./example.txt') print(type(path)) # output is a pathlib object #

This confirms that you created a Path object.

Let’s see how to use the pathlib module to check if a file exists using the is_file() method, one of the built-in methods available with the pathlib module.

How to Check if a File Exists Using the Path.is_file() Method in Python

The is_file() method checks if a file exists.

It returns True if the Path object points to a file and False if the file doesn’t exist.

Let’s see an example of how it works:

from pathlib import Path # create a Path object with the path to the file path = Path('./example.txt') print(path.is_file()) # output # True 

Since the example.txt file exists in the specified path, the is_file() method returns True .

Conclusion

In this article, you learned how to check if a file exists in Python using the os.path and pathlib modules and their associated methods.

Hopefully, you have understood the differences between the modules and when to use each one.

Thank you for reading, and happy coding!

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