A simple file downloader for Python

downloader.py

import os
import requests


def download_file(url, folder, filename):
    """Downloads a file from the internet, but only if it doesn't already exist on disk.

    Parameters
    ----------
    url : str
      The URL to download.
    folder : list or tuple
      The folder where to store the file, as list.
      For example, use [".", "files", "model"] instead of "./files/model/".
    filename : str
      The name of the file on disk.

    Example
    -------

    >>> download_file(
    ...     'https://upload.wikimedia.org/wikipedia/commons/0/0e/Tree_example_VIS.jpg',
    ...     ('.', 'foo', 'bar'),
    ...     'example.jpg')

    """
    full_filepath = os.path.abspath(os.path.expanduser(os.path.expandvars(
        os.path.join(*tuple(folder)))))

    full_filename = os.path.join(full_filepath, filename)

    if os.path.isfile(full_filename):
        return

    os.makedirs(full_filepath, exist_ok=True)

    resp = requests.get(url, stream=True)

    with open(full_filename, 'wb') as file_desc:
        for chunk in resp.iter_content(chunk_size=5000000):
            file_desc.write(chunk)