How to use the qtconsole.qt.QtGui.QFontMetrics function in qtconsole

def _set_font(self, font):
        """ Sets the base font for the ConsoleWidget to the specified QFont.
        """
        font_metrics = QtGui.QFontMetrics(font)
        self._control.setTabStopWidth(self.tab_width * font_metrics.width(' '))

        self._completion_widget.setFont(font)
        self._control.document().setDefaultFont(font)
        if self._page_control:
            self._page_control.document().setDefaultFont(font)

        self.font_changed.emit(font)

def _page(self, text, html=False):
        """ Displays text using the pager if it exceeds the height of the
        viewport.

        Parameters
        ----------
        html : bool, optional (default False)
            If set, the text will be interpreted as HTML instead of plain text.
        """
        line_height = QtGui.QFontMetrics(self.font).height()
        minlines = self._control.viewport().height() / line_height
        if self.paging != 'none' and \
                re.match("(?:[^\n]*\n){%i}" % minlines, text):
            if self.paging == 'custom':
                self.custom_page_requested.emit(text)
            else:
                # disable buffer truncation during paging
                self._control.document().setMaximumBlockCount(0)
                self._page_control.clear()
                cursor = self._page_control.textCursor()
                if html:
                    self._insert_html(cursor, text)
                else:
                    self._insert_plain_text(cursor, text)
                self._page_control.moveCursor(QtGui.QTextCursor.Start)

Parameters
        ----------
        items : sequence of strings
            The strings to process.

        separator : str, optional [default is two spaces]
            The string that separates columns.

        Returns
        -------
        The formatted string.
        """
        # Calculate the number of characters available.
        width = self._control.document().textWidth()
        char_width = QtGui.QFontMetrics(self.font).width(' ')
        displaywidth = max(10, (width / char_width) - 1)

        return columnize(items, separator, displaywidth)

def show_items(self, cursor, items, prefix_length=0):
        """ Shows the completion widget with 'items' at the position specified
            by 'cursor'.
        """
        if not items :
            return
        # Move cursor to start of the prefix to replace it
        # when a item is selected
        cursor.movePosition(QtGui.QTextCursor.Left, n=prefix_length)
        self._start_position = cursor.position()
        self._consecutive_tab = 1
        # Calculate the number of characters available.
        width = self._text_edit.document().textWidth()
        char_width = QtGui.QFontMetrics(self._console_widget.font).width(' ')
        displaywidth = int(max(10, (width / char_width) - 1))
        items_m, ci = text.compute_item_matrix(items, empty=' ',
                                               displaywidth=displaywidth)
        self._sliding_interval = SlidingInterval(len(items_m)-1)

        self._items = items_m
        self._size = (ci['rows_numbers'], ci['columns_numbers'])
        self._old_cursor = cursor
        self._index = (0, 0)
        sjoin = lambda x : [ y.ljust(w, ' ') for y, w in zip(x, ci['columns_width'])]
        self._justified_items = list(map(sjoin, items_m))
        self._update_list(hilight=False)

def sizeHint(self):
        """ Reimplemented to suggest a size that is 80 characters wide and
            25 lines high.
        """
        font_metrics = QtGui.QFontMetrics(self.font)
        margin = (self._control.frameWidth() +
                  self._control.document().documentMargin()) * 2
        style = self.style()
        splitwidth = style.pixelMetric(QtGui.QStyle.PM_SplitterWidth)

        # Note 1: Despite my best efforts to take the various margins into
        # account, the width is still coming out a bit too small, so we include
        # a fudge factor of one character here.
        # Note 2: QFontMetrics.maxWidth is not used here or anywhere else due
        # to a Qt bug on certain Mac OS systems where it returns 0.
        width = font_metrics.width(' ') * self.width + margin
        width += style.pixelMetric(QtGui.QStyle.PM_ScrollBarExtent)
        if self.paging == 'hsplit':
            width = width * 2 + splitwidth

        height = font_metrics.height() * self.height + margin

def _set_tab_width(self, tab_width):
        """ Sets the width (in terms of space characters) for tab characters.
        """
        font_metrics = QtGui.QFontMetrics(self.font)
        self._control.setTabStopWidth(tab_width * font_metrics.width(' '))

        self._tab_width = tab_width