pypandoc | Convert multiple files

Objective:

I want to use Pypandoc to create a function where the user inputs three arguments being: (i) an input folder; (ii) a file format to convert to; and (iii) an output folder.

Problem:

Before I convert this to a loop to convert multiple files, I want to get it working with one file. The code runs from the following directory:

*C:\workspace\code\doc_check\venv\Scripts\*

The directory containing the files to convert is:

*C:\workspace\code\doc_check\test_folder*

The directory I want to output to is:

*C:\workspace\code\doc_check\output*

Here is my code, followed by the error message I keep receiving:

import pypandoc
import os

# Convert Word document to .md using pypandoc.

def convert(input_dir, output_format, output_dir):
    data_files = os.listdir(input_dir)
    path_name = os.path.join(input_dir, data_files[0])
    output = pypandoc.convert_file(path_name, output_format, outputfile=output_dir + 'test_doc.md')
    return output

convert('test_folder', 'md', 'output')

Error message:

C:\workspace\code\doc_check\venv\Scripts\python.exe C:/workspace/code/doc_check/venv/Scripts/doc_check.py
Traceback (most recent call last):
  File "C:/workspace/code/doc_check/venv/Scripts/doc_check.py", line 18, in <module>
    convert('test_folder', 'md', 'output')
  File "C:/workspace/code/doc_check/venv/Scripts/doc_check.py", line 7, in convert
    data_files = os.listdir(input_dir)
FileNotFoundError: [WinError 3] The system cannot find the path specified: 'test_folder'