def get_min_x_y_coord(city):
    """
    Returns min x- and y-coordinates as tuple, found within city object.

    Requires position parameter (shapely point) on every node!

    Parameters
    ----------
    city : object
        City object of pycity_calc

    Returns
    -------
    tuple_min : tuple (of floats)
        Tuple holding minimal x-/y-coordinates (x_min, y_min)
    """

    x_min = None
    y_min = None

    #  Find min x and y coordinate
    for n in city.nodes():
        x_curr = city.nodes[n]['position'].x
        y_curr = city.nodes[n]['position'].y

        if x_min is None or x_min > x_curr:
            x_min = x_curr

        if y_min is None or y_min > y_curr:
            y_min = y_curr

    tuple_min = (x_min, y_min)

    return tuple_min