Stretch table column in Reportlab

Question

I'm trying to stretch a table column in Reportlab (not RML), I've tried setting colWidths like this:

tab = Table(data, colWidths=["*", None, None, None, None, None])

as written in the documentation, but the size of the first column doesn't change (it stays on "size-to-contents"). Is there any way to make the first column stretch to available space, without specifying a fixed size? (since the other columns will change dynamically depending on some parameters)

Answer 1

This seems to be a deliberate behavior of Reportlab, since the width calculation code says this:

def _calc_pc(V,avail):
    '''check list V for percentage or * values
    1) absolute values go through unchanged
    2) percentages are used as weights for unconsu
    3) if no None values were seen '*' weights are
    set equally with unclaimed space
    otherwise * weights are assigned as None'''

Which means that * and None can't be used together in the list of widths, which doesn't make sense because then how do you make a column stretch while the other are sized to content. Anyways, I ended up writting a wrapper function that re-calculates everything:

def table_fix(data, cols, total):
    table = Table(data, colWidths=cols)
    res = list(cols)
    val = table._cellvalues
    style = table._cellStyles
    while None in res:
        idx = res.index(None)
        width = 0
        for i, vi in enumerate(val):
            v = vi[idx]
            s = style[i][idx]
            nw = table._elementWidth(v, s) + s.leftPadding + s.rightPadding
            if nw > width:
                width = nw
        res[idx] = width
    table._colWidths = table._argW = res
    return table

Ugly but does the job for me. It can be extended to support multiple * columns if need be.