Conditionally Color Table Cells with ReportLab - python-3.x

Question

I've created a table using ReportLab. I would like to conditionally color the cells, depending on their contents (in my case, I want negative numbers to be red). To be clear, I have the conditional code working, I can't figure out how to add color. What I've tried:
using the <font color="..."> tag. Instead, the tags is included verbatim in the output.
wrapping each cell in Paragraph(...) (suggested in this answer). In this case, the cell text is linewrapped after each letter.
wrapping the table in Paragraph(...). In this case, reportlab errors out (I believe the resulting error was TypeError: split() missing required positional argument: 'availHeight')
I found reportlab.platypus.tables.CellStyle in the reportlab source code, but can't figure out make use of it. Google turns up nothing useful and it's not mentioned in the reportlab documentation.
I guess TableStyle(...) rules could be used, but the cells aren't in a predetermined position within the table (which is what all the examples assume).
Help appreciated!

Answer 1

Using TableStyle() would be an acceptable solution. You could loop through the data and add a style command when the condition is met.
Here is an example:
import random
from reportlab.lib.pagesizes import letter
from reportlab.lib.colors import red
from reportlab.platypus import SimpleDocTemplate, Table, TableStyle
# Generate random data with positive and negative values as list of lists.
data = []
for _ in range(20):
data.append(random.sample(range(-10, 10), 5))
table_style = TableStyle([('ALIGN', (0, 0), (-1, -1), 'RIGHT')])
# Loop through list of lists creating styles for cells with negative value.
for row, values, in enumerate(data):
for column, value in enumerate(values):
if value < 0:
table_style.add('TEXTCOLOR', (column, row), (column, row), red)
table = Table(data)
table.setStyle(table_style)
pdf = SimpleDocTemplate('example.pdf', pagesize=letter)
pdf.build([table])