Download files from a list if not already downloaded

I can do this in c#, and the code is pretty long.

Would be cool if someone can show me how this would be done via python.

Pseudo code is:

url: www.example.com/somefolder/filename1.pdf1. load file into an array (file contains a url on each line)2. if file e.g. filename1.pdf doesn't exist, download file

The script can be in the following layout:

/python-downloader//python-downloader/dl.py/python-downloader/urls.txt/python-downloader/downloaded/filename1.pdf