def _compute_cols_width(self):
        """Return an array with the width of each column

        If a specific width has been specified, exit. If the total of the
        columns width exceed the table desired width, another width will be
        computed to fit, and cells will be wrapped.
        """

        if hasattr(self, "_width"):
            return
        maxi = []
        if self._header:
            maxi = [ self._len_cell(x) for x in self._header ]
        for row in self._rows:
            for cell,i in zip(row, range(len(row))):
                try:
                    maxi[i] = max(maxi[i], self._len_cell(cell))
                except (TypeError, IndexError):
                    maxi.append(self._len_cell(cell))
        items = len(maxi)
        length = reduce(lambda x,y: x+y, maxi)
        if self._max_width and length + items*3 + 1 > self._max_width:
            maxi = [(self._max_width - items*3 -1) / items \
                for n in range(items)]
        self._width = maxi