def download_file(url, dest=None, chunk_size=1024, replace="ask",
                  label="Downloading {dest_basename} ({size:.2f}MB)",
                  expected_extension=None):
    """Download a file from a given URL and display progress.

    :param dest: If the destination exists and is a directory, the filename
        will be guessed from the Content-Disposition header. If the destination
        is an existing file, the user will either be prompted to overwrite, or
        the file will be replaced (depending on the value of **replace**). If
        the destination does not exist, it will be used as the filename.
    :param int chunk_size: bytes read in at a time.
    :param replace: If `False`, an existing destination file will not be
        overwritten.
    :param label: a string which is formatted and displayed as the progress bar
        label. Variables provided include *dest_basename*, *dest*, and *size*.
    :param expected_extension: if set, the filename will be sanitized to ensure
        it has the given extension. The extension should not start with a dot
        (`.`).
    """
    dest = Path(dest or url.split("/")[-1])
    response = get(url, stream=True)
    if (dest.exists()
            and dest.is_dir()
            and "Content-Disposition" in response.headers):
        content_disposition = rfc6266.parse_requests_response(response)
        if expected_extension is not None:
            filename = content_disposition.filename_sanitized(
                expected_extension)
        filename = secure_filename(filename)
        dest = dest / filename
    if dest.exists() and not dest.is_dir():
        if (replace is False
                or replace == "ask"
                and not click.confirm("Replace {}?".format(dest))):
            return str(dest)
    size = int(response.headers.get("content-length", 0))
    label = label.format(dest=dest, dest_basename=dest.name,
                         size=size/1024.0/1024)
    with click.open_file(str(dest), "wb") as f:
        content_iter = response.iter_content(chunk_size=chunk_size)
        with click.progressbar(content_iter, length=size/1024,
                               label=label) as bar:
            for chunk in bar:
                if chunk:
                    f.write(chunk)
                    f.flush()
    return str(dest)
def characteristics(char, title=''):
    fig, axs = plt.subplots(2, 2, figsize=(10, 8), sharex=True)
    if title:
        fig.suptitle(title)

    n = np.array(char['n'])*60
    pmech = np.array(char['pmech'])*1e-3

    axs[0, 0].plot(n, np.array(char['T']), 'C0-', label='Torque')
    axs[0, 0].set_ylabel("Torque / Nm")
    axs[0, 0].grid()
    axs[0, 0].legend(loc='center left')
    ax1 = axs[0, 0].twinx()
    ax1.plot(n, pmech, 'C1-', label='P mech')
    ax1.set_ylabel("Power / kW")
    ax1.legend(loc='lower center')

    axs[0, 1].plot(n[1:], np.array(char['u1'][1:]), 'C0-', label='Voltage')
    axs[0, 1].set_ylabel("Voltage / V",)
    axs[0, 1].grid()
    axs[0, 1].legend(loc='center left')
    ax2 = axs[0, 1].twinx()
    ax2.plot(n[1:], char['cosphi'][1:], 'C1-', label='Cos Phi')
    ax2.set_ylabel("Cos Phi")
    ax2.legend(loc='lower right')

    if 'id' in char:
        axs[1, 0].plot(n, np.array(char['id']), label='Id')
    if 'iq' in char:
        axs[1, 0].plot(n, np.array(char['iq']), label='Iq')
    axs[1, 0].plot(n, np.array(char['i1']), label='I1')
    axs[1, 0].set_xlabel("Speed / rpm")
    axs[1, 0].set_ylabel("Current / A")
    axs[1, 0].legend(loc='center left')
    if 'beta' in char:
        ax3 = axs[1, 0].twinx()
        ax3.plot(n, char['beta'], 'C3-', label='Beta')
        ax3.set_ylabel("Beta / °")
        ax3.legend(loc='center right')
    axs[1, 0].grid()

    plfe = np.array(char['plfe'])*1e-3
    plcu = np.array(char['plcu'])*1e-3
    pl = np.array(char['losses'])*1e-3
    axs[1, 1].plot(n, plcu, 'C0-', label='Cu Losses')
    axs[1, 1].plot(n, plfe, 'C1-', label='Fe Losses')
    axs[1, 1].set_ylabel("Losses / kW")
    axs[1, 1].legend(loc='center left')
    axs[1, 1].grid()
    axs[1, 1].set_xlabel("Speed / rpm")
    ax4 = axs[1, 1].twinx()
    ax4.plot(n[1:-1], char['eta'][1:-1], 'C3-', label="Eta")
    ax4.legend(loc='upper center')
    ax4.set_ylabel("Efficiency")

    fig.tight_layout()