def modify_axes(ax=None,xticks=[],xt_labels=[],xlim=[],\
            yticks=[],yt_labels=[],ylim=[],xlabel=None,ylabel=None,\
            vlines=True,zeroline=True):
    """
    - Returns None, applies given settings on axes. Prefered to use before other plotting.
    - **Parameters**
        - ax  : Matplotlib axes object.
        - (x,y)ticks : List of positions on (x,y axes).
        - (xt,yt)_labels : List of labels on (x,y) ticks points.
        - (x,y)lim : [min, max] of (x,y) axes.
        - (x,y)label : axes labels.
        - vlines : If true, drawn when `ylim` is not empty.
        - zeroline : If True, drawn when `xlim` is not empty.
    """
    if ax==None:
        raise ValueError("Matplotlib axes (ax) is not given.")
    else:
        if xticks:
            ax.set_xticks(xticks)
            ax.set_xticklabels(xt_labels)
        if yticks:
            ax.set_yticks(yticks)
            ax.set_yticklabels(yt_labels)
        if xlim:
            ax.set_xlim(xlim)
            if zeroline:
                ax.hlines(0,min(xlim),max(xlim),color=(0,0,0,0.6), linestyle='dashed',lw=0.3)
        if ylim:
            ax.set_ylim(ylim)
            if vlines:
                ax.xaxis.grid(color=(0,0,0,0.6), linestyle='dashed',lw=0.3)
        if xlabel!=None:
            ax.set_xlabel(xlabel)
        if ylabel!=None:
            ax.set_ylabel(ylabel)
        ax.tick_params(direction='in', top=True,bottom=True,left=True,right=True,length=4, width=0.3, grid_alpha=0.8)
    return None