[Python] Python Debugging Behavior Different From C# Implementation of Python

I have a script that is just trying to check if an Excel file is encrypted with a password. The purpose is that I am building a GUI that will toggle a password UI element to the user (sometimes the file that will be inputted is not encrypted).

My problem is that when I am debugging in VS Code, the code behaves as expected. But then I tried packaging into an exe using pyinstaller and call it in C#, the behavior changes to an DecryptionError instead of InvalidKeyError. This current iteration then used my venv while calling the python file directly. Same result, unfortunately.

Initially, I was trying to get this feature to work within C#, but was unable, so I went through this Python approach. If there are better solutions, I am open for it

Here's my quick Python script:

import io
import msoffcrypto
import argparse

from msoffcrypto.exceptions import InvalidKeyError, DecryptionError

if __name__ == '__main__':
parser= parser = argparse.ArgumentParser()

parser.add_argument('--filepath', required=True, help='Path to the encrypted Office file')
parser.add_argument('--test_string', required=True, help='Password to test against the encrypted file')

args = parser.parse_args()
file_path = args.filepath
test_pass = args.test_string

print(f'Checking file: {file_path} with password: {test_pass}')

try:
# Attempt to open the file and decrypt it with the pseudo password
with open(file_path, 'rb') as f:
office_file = msoffcryptfficeFile(f)
office_file.load_key(password=test_pass)
decrypted = io.BytesIO()
office_file.decrypt(decrypted)

# Case where there is password encryption
except InvalidKeyError:
print(True)

# Case where there is NOT password encryption
except DecryptionError as e:
print(False)

# Edge case
except Exception as e:
print(False)


Here's my C# implementation:

private static bool IsExcelFilePasswordProtected(string filePath)
{
string venvPython = Path.Combine(AppContext.BaseDirectory, "venv", "Scripts", "python.exe"); // Windows
string scriptPath = Path.Combine(AppContext.BaseDirectory, "CheckPass.py");
string args = $"\"{scriptPath}\" --filepath \"{filePath}\" --test_string notapassword";

var psi = new ProcessStartInfo
{
FileName = venvPython,
Arguments = args,
RedirectStandardOutput = true,
UseShellExecute = false,
CreateNoWindow = true
};

try
{
using (var process = Process.Start(psi))
{
string output = process?.StandardOutput.ReadToEnd() ?? string.Empty;
process?.WaitForExit();
bool hasPassword = bool.TryParse(output.Trim(), out bool result) && result;
return hasPassword;
}
}
catch (Exception e)
{
return false;
}
}

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