Python check if file extension

Python OS Check: Methods to Verify File Existence by Extension

Learn how to check if a file with a specific extension exists in a directory using Python’s OS module. Explore methods like os.path.isfile(), os.path.splitext(), os.listdir() and endswith(), creating a function to check if a file exists without looking at its extension, and using regular expressions with Glob.

• Using os.path.isfile() to check if a file exists
• Using os.path.splitext() to check file extension
• Using os.listdir() and endswith() to list files with a specific extension
• Creating a function to check if a file exists without looking at its extension
• Using regular expressions with Glob to check for a specific extension
• Other helpful code examples for checking if a file with a specific extension exists using Python’s OS module
• Conclusion
• How do you check if a file has an extension?
• How do I check if a file exists using an exception in Python?
• How do you check if there exist a file in Python?
• How do I know if a file has no extension Python?

Python’s OS module is a powerful tool for working with files and directories. One common task is to check if a file with a specific extension exists in a directory. In this blog post, we’ll explore several methods for doing this using Python’s OS module.

Using os.path.isfile() to check if a file exists

The os.path.isfile() function can be used to check if a file exists in a directory. This function returns True if the path exists and is a file, or False otherwise. To check if a file with a specific extension exists, we can use os.path.join() to create the path and os.path.isfile() to check if it exists.

import osfile_name = 'example.txt' dir_name = '/path/to/directory'path = os.path.join(dir_name, file_name) exists = os.path.isfile(path)if exists: print(f'file_name> exists in dir_name>') else: print(f'file_name> does not exist in dir_name>') 

In this example, we create a path using os.path.join() and check if the file exists using os.path.isfile() . If the file exists, we print a message indicating that it exists in the specified directory. Otherwise, we print a message indicating that it does not exist in the specified directory.

Using os.path.splitext() to check file extension

The os.path.splitext() function can be used to split a path into a root and extension. This function returns a tuple containing the root and extension of the path. By checking the extension of a file using os.path.splitext() , we can determine if it has the desired extension.

import osfile_name = 'example.txt'root, ext = os.path.splitext(file_name)if ext == '.txt': print(f'file_name> has the desired extension') else: print(f'file_name> does not have the desired extension') 

In this example, we use os.path.splitext() to split the file name into its root and extension. We then check if the extension is .txt using an if statement. If the extension is .txt , we print a message indicating that the file has the desired extension. Otherwise, we print a message indicating that the file does not have the desired extension.

Using os.listdir() and endswith() to list files with a specific extension

The os.listdir() function can be used to list all files in a directory. By iterating over the list and using the endswith() function, we can check if each file has the desired extension. This method is useful if we want to list all files with a specific extension in a directory.

import osdir_name = '/path/to/directory' extension = '.txt'for file_name in os.listdir(dir_name): if file_name.endswith(extension): print(f'file_name> has the desired extension') else: print(f'file_name> does not have the desired extension') 

In this example, we use os.listdir() to list all files in a directory. We then iterate over the list and check if each file has the desired extension using endswith() . If a file has the desired extension, we print a message indicating that it has the desired extension. Otherwise, we print a message indicating that it does not have the desired extension.

Creating a function to check if a file exists without looking at its extension

If we want to check if a file exists without looking at its extension, we can create a function with the desired file name. This function can use os.path.join() and os.path.isfile() to check if the file exists. This method is useful if we know the name of the file but not its extension.

import osdef file_exists(file_name, dir_name): path = os.path.join(dir_name, file_name) return os.path.isfile(path)file_name = 'example' dir_name = '/path/to/directory'exists = file_exists(file_name, dir_name)if exists: print(f'file_name> exists in dir_name>') else: print(f'file_name> does not exist in dir_name>') 

In this example, we define a function called file_exists() that takes a file name and directory name as arguments. The function uses os.path.join() to create a path and os.path.isfile() to check if the file exists. We then call the function with the desired file name and directory name and print a message indicating whether the file exists in the directory or not.

Using regular expressions with Glob to check for a specific extension

Glob can be used to search for files with a specific pattern. By using regular expressions with Glob, we can search for files with a specific extension. This method is useful if we want to search for files with a specific extension in a directory and its subdirectories.

import globdir_name = '/path/to/directory' extension = '*.txt'for file_name in glob.glob(os.path.join(dir_name, extension), recursive=True): print(file_name) 

In this example, we use glob.glob() to search for files with the extension .txt in the directory /path/to/directory and its subdirectories. We use os.path.join() to create the path and the recursive=True parameter to search in subdirectories. The function returns a list of file names that match the pattern, which we print to the console.

Other helpful code examples for checking if a file with a specific extension exists using Python’s OS module

In python, python os check if file with extension exists code example

import os if any(File.endswith(".txt") for File in os.listdir(".")): print("true") else: print("false")

Conclusion

Python’s OS module provides several methods for checking if a file with a specific extension exists in a directory. The methods discussed in this blog post include os.path.isfile() , os.path.splitext() , os.listdir() and endswith() , creating a function to check if a file exists without looking at its extension, and using regular expressions with Glob. By using these methods, we can easily check if a file with a specific extension exists and perform further operations on it.

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Checking File Extension in Python for Python Files

To learn more about the Path class, it may be beneficial to read the manual page available at https://docs.python.org/3/library/pathlib.html. For those seeking to convert symlinks to real files, a script in the python tools library may be useful. To determine if a directory entry is a symlink, one can use the method provided in Solution 1. For Python 3.4 and higher versions, the Path class in Solution 2 can be used with caution when using the is_symlink() method.

Python argparse file extension checking

Certainly, all you have to do is designate a suitable function as the type .

import argparse import os.path parser = argparse.ArgumentParser() def file_choices(choices,fname): ext = os.path.splitext(fname)[1][1:] if ext not in choices: parser.error("file doesn't end with one of <>".format(choices)) return fname parser.add_argument('fn',type=lambda s:file_choices(("csv","tab"),s)) parser.parse_args() 

temp $ python test.py test.csv temp $ python test.py test.foo usage: test.py [-h] fn test.py: error: file doesn't end with one of ('csv', 'tab') 

Here’s a potentially cleaner and more universal approach to accomplish the task.

import argparse import os.path def CheckExt(choices): class Act(argparse.Action): def __call__(self,parser,namespace,fname,option_string=None): ext = os.path.splitext(fname)[1][1:] if ext not in choices: option_string = '(<>)'.format(option_string) if option_string else '' parser.error("file doesn't end with one of <><>".format(choices,option_string)) else: setattr(namespace,self.dest,fname) return Act parser = argparse.ArgumentParser() parser.add_argument('fn',action=CheckExt()) print parser.parse_args() 

While the interface becomes much cleaner when formatting arguments, the code becomes somewhat more intricate.

Create a personalized function that accepts a string as input. Remove the extension for comparison purposes and if the string is satisfactory, return it. However, if it doesn’t meet the criteria, raise the exception that argparse requires.

def valid_file(param): base, ext = os.path.splitext(param) if ext.lower() not in ('.csv', '.tab'): raise argparse.ArgumentTypeError('File must have a csv or tab extension') return param 

Subsequently, employ said function, for instance:

parser = argparse.ArgumentParser() parser.add_argument('filename', type=valid_file) 

It is not necessary to provide a specific object to the choices argument; instead, any container that supports the «in» operator can be used. Additional information on this topic can be found in the pydocs.

It is possible for you to verify it on your own and offer input to the user as well.

Check if object is file-like in Python, File-like objects are objects in Python that behave like a real file, e.g. have a read() and a write method(), but have a different implementation from file.It is realization of the Duck Typing concept.. It is considered a good practice to allow a file-like object everywhere where a file is expected so that e.g. a StringIO or a …

How to check if entry is file or folder using Python’s standard library zipfile?

Have you considered verifying whether the file name concludes with / ?

Python program to find files having a particular, This program searches for the files having “.xml” extension from a list of different files. Make a regular expression/pattern : “\.xml$”. Here re.search () function is used to check for a match anywhere in the string (name of the file). It basically returns the match object when the pattern is found and if the pattern is …

How to check if file is a symlink in Python?

Use the following method to check if a directory entry is a symbolic link.

os.path.islink(path)

Determine whether the path points to a directory entry that is a symbolic link and return True. If symbolic links are not supported, the result will always be False.

drwxr-xr-x 2 root root 4096 2011-11-10 08:14 bin/ drwxrwxrwx 1 root root 57 2011-07-10 05:11 initrd.img -> boot/initrd.img-2.. >>> import os.path >>> os.path.islink('initrd.img') True >>> os.path.islink('bin') False 

The Path class is available for use in Python 3.4 and later versions.

from pathlib import Path # rpd is a symbolic link >>> Path('rdp').is_symlink() True >>> Path('README').is_symlink() False 

Caution is necessary while using the is_symlink() function as it can yield a True output irrespective of the link’s target existence, as long as the object is named a symlink. This applies to Linux/Unix platforms.

ln -s ../nonexistentfile flnk 

Launch Python in your present working directory.

>>> from pathlib import Path >>> Path('flnk').is_symlink() True >>> Path('flnk').exists() False 

The Path class manual page at https://docs.python.org/3/library/pathlib.html is worth reading for the programmer who needs to make a decision on their requirements as Python 3 has renamed many classes.

In an effort to avoid excessive elaboration, I stumbled upon this page while searching for symlinks to transform into actual files. It was here that I discovered a script located within the python tools library.

#Source https://github.com/python/cpython/blob/master/Tools/scripts/mkreal.py import sys import os from stat import * BUFSIZE = 32*1024 def mkrealfile(name): st = os.stat(name) # Get the mode mode = S_IMODE(st[ST_MODE]) linkto = os.readlink(name) # Make sure again it's a symlink f_in = open(name, 'r') # This ensures it's a file os.unlink(name) f_out = open(name, 'w') while 1: buf = f_in.read(BUFSIZE) if not buf: break f_out.write(buf) del f_out # Flush data to disk before changing mode os.chmod(name, mode) mkrealfile("/Users/test/mysymlink") 

Python — Check if a file type is a media file?, If you want to create a module that checks if the file is a media file you need to call the init function at the start of the module. Here is an example of how to create the module: ismediafile.py

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