How to exclude blank cell in conditional formatting in openpyxl?

Question

I am using conditional formatting in openpyxl but got stumped trying to exclude blank cells. I have a column with numbers which I format using CellisRule. Code I use is below.

ws2.conditional_formatting.add('C3:C25',CellIsRule(operator='lessThan', formula=['85'], stopIfTrue=True, fill=redFill,font=whiteText))

ws2.conditional_formatting.add('C3:C25',CellIsRule(operator='greaterThan', formula=['89.99'], stopIfTrue=True, fill=greenFill))

ws2.conditional_formatting.add('C3:C25',CellIsRule(operator='between', formula=['85', '89.99'], stopIfTrue=True, fill=yellowFill))

I tried to use FormulaRule but got no idea to use for the formula.

Update:

Instead of using conditional formatting, using a for loop worked.

for row in ws2.iter_rows("C3:C25"):
    for cell in row:
        if cell.value == None:
            set_stylewhite(cell)
        elif cell.value >= 90:
            set_stylegreen(cell)
        elif cell.value <= 85:
            set_stylered(cell)
        else:
            set_styleyellow(cell)

Answer 1

If you're using a formula then you should use the an expression type rule. In general, it's always better to compose the rules and styles separately:

from openpyxl import Workbook
from openpyxl.formatting.rule import Rule
from openpyxl.styles.differential import DifferentialStyle
from openpyxl.styles import Font, PatternFill

red_text = Font(color="9C0006")
red_fill = PatternFill(bgColor="FFC7CE")
dxf = DifferentialStyle(font=red_text, fill=red_fill)

r = Rule(type="expression", dxf=dxf)
r.formula = ["NOT(ISBLANK(A1))"]

wb = Workbook()
ws = wb.active

for v in range(10):
    ws.append([v])

ws['A4'] = None
ws.conditional_formatting.add("A1:A10".format(ws.max_row), r)
wb.save("sample.xlsx")