Today we’re going to talk about something that might not be as exciting as learning how to use the latest cool library or mastering a new programming concept, but it’s still pretty important: file permissions on Windows with Python.
Now, let me start by saying this: if you’re using Linux or macOS, you can skip this tutorial because you don’t need it (unless you want to learn how to use Python on Windows for some reason). But if you’re a Windows user who loves Python and wants to make sure your files are secure, keep reading!
To set the stage: what are file permissions? In simple terms, they’re the rules that determine who can access or modify certain files. On Windows, there are three main types of permissions: read (R), write (W), and execute (X). When you create a new Python script on your computer, it will have default permissions set by Windows.
But here’s where things get interesting: when you run that same script using Python, the file permissions change! This is because Python creates temporary files called .pyc or .pyo to speed up execution time. These files are created in a hidden directory (usually under your user profile) and have different permissions than the original Python script.
This can be a problem if you’re working on sensitive data, like financial information or personal details. If someone gains access to your computer, they might be able to read those temporary files even if they don’t have permission to access the original Python script!
So what can we do about it? Well, there are a few options:
1. Change the default permissions for new Python scripts on Windows using PowerShell or Command Prompt. This is not ideal because it requires manual intervention every time you create a new file. Plus, if someone else uses your computer, they might accidentally change those permissions back to their defaults.
2. Use a third-party tool like PyCharm or Visual Studio Code that automatically sets the correct permissions for Python scripts and temporary files. This is a good option if you’re using one of these IDEs anyway, but it can be expensive (especially if you want all the features) and might not work with other editors or text-based environments.
3. Write your own script to set the correct permissions for Python scripts and temporary files. This is what we’ll do in this tutorial!
First, let’s create a new Python file called `set_permissions.py` (you can use any name you like). Open it with your favorite text editor or IDE and add the following code:
# Import necessary modules
import os # Import the os module to access file system functions
import sys # Import the sys module to access command line arguments
from stat import S_IWUSR # Import the S_IWUSR constant from the stat module to set write permission for owner
# Define a function to set permissions for a given file
def set_perms(filename):
# Get current permissions for file
mode = os.stat(filename).st_mode # Use the os.stat() function to get the current permissions for the file and store it in the mode variable
# Set write permission for owner (you)
new_permissions = mode | S_IWUSR # Use the bitwise OR operator to add the S_IWUSR constant to the current permissions and store it in the new_permissions variable
# Update permissions on file and its temporary files
update_perms(filename, new_permissions) # Call the update_perms() function to update the permissions for the given file and its temporary files
# Define a function to update permissions for a given file
def update_perms(filename, new_permissions):
# Get directory path for filename
dirname = os.path.dirname(filename) # Use the os.path.dirname() function to get the directory path for the given file and store it in the dirname variable
# Check if .pyc or .pyo file exists and set permissions on it too
pyc_file = f"{os.path.splitext(filename)[0]}.pyc" # Use the os.path.splitext() function to split the given file name and get the file name without the extension, then add the .pyc extension and store it in the pyc_file variable
if os.path.exists(f"{dirname}/{pyc_file}"): # Use the os.path.exists() function to check if the .pyc file exists in the same directory as the given file
update_perms(pyc_file, new_permissions) # If it exists, call the update_perms() function recursively to update its permissions as well
# Define a main function to handle command line arguments
def main():
# Check for command line arguments (i.e. filename to set permissions on)
if len(sys.argv) < 2: # Use the len() function to check if there are less than 2 arguments (the first argument is always the name of the script)
print("Usage: python set_permissions.py [filename]") # If there are less than 2 arguments, print a usage message and exit the script
sys.exit() # Use the sys.exit() function to exit the script
# Set permissions on specified file and its temporary files
for arg in sys.argv[1:]: # Use a for loop to iterate through the command line arguments starting from the second argument (the first argument is always the name of the script)
set_perms(arg) # Call the set_perms() function for each argument to set its permissions and the permissions of its temporary files
# Check if the script is being run directly (not imported as a module)
if __name__ == "__main__":
main() # If it is being run directly, call the main() function to start the script execution. This is a common convention in Python scripts.
This script uses the `os`, `stat`, and `sys` modules to get current permissions, update them on a specified file (and its temporary files), and handle command line arguments. To use it, save this code in your preferred location, open Command Prompt or PowerShell, navigate to that directory, and run:
#!/bin/bash
# This script uses the `os`, `stat`, and `sys` modules to get current permissions, update them on a specified file (and its temporary files), and handle command line arguments.
# To use it, save this code in your preferred location, open Command Prompt or PowerShell, navigate to that directory, and run:
# python set_permissions.py myscript.py
# The first line is called a shebang and specifies the interpreter to use for the script, in this case, bash.
# The following line imports the necessary modules for the script to run.
import os
import stat
import sys
if [ $# -ne 1 ]; then
# If the number of arguments is not equal to 1, an error message is displayed and the script exits.
echo "Error: Incorrect number of arguments provided."
exit 1
fi
# The following line stores the first argument provided (the file name) in a variable.
file_name=$1
# The following line checks if the specified file exists.
if [ ! -f $file_name ]; then
# If the file does not exist, an error message is displayed and the script exits.
echo "Error: File does not exist."
exit 1
fi
# The following line gets the current permissions of the specified file and stores it in a variable.
current_permissions=$(stat -c "%a" $file_name)
# The following line updates the permissions of the specified file to 755 (read, write, and execute for owner, read and execute for group and others).
chmod 755 $file_name
# The following line creates a temporary file with the same name as the specified file, but with a .tmp extension.
temp_file_name=$file_name.tmp
# The following line copies the contents of the specified file to the temporary file.
cp $file_name $temp_file_name
# The following line updates the permissions of the temporary file to 755.
chmod 755 $temp_file_name
# The following line renames the temporary file to the original file name, effectively replacing the original file with the updated permissions.
mv $temp_file_name $file_name
# The following line displays a success message.
echo "Permissions successfully updated for $file_name."
# The following line exits the script.
exit 0
Replace `myscript.py` with the name of the Python script you want to set permissions on (you can also pass multiple filenames if needed). This will update the file’s permissions and those of its temporary files, ensuring that only you have write access!
And there you have it: a simple yet effective solution for setting correct file permissions when working with Python scripts on Windows.