Rule-based symbology based on given table

Question

I would like to ask if it's somehow possible to create script with rule-based symbology in QGIS which would be based on expressions given from separate table (for example CSV, or Excel sheet). I used code given from user eurojam:

def rule_based_style(layer, symbol, label, expression, color):
    root_rule = renderer.rootRule()
    rule = root_rule.children()[0].clone()
    rule.setLabel(label)
    rule.setFilterExpression(expression)
    rule.symbol().setColor(QColor(color))
    root_rule.appendChild(rule)

layer = iface.activeLayer() 
symbol = QgsSymbol.defaultSymbol(layer.geometryType())
renderer = QgsRuleBasedRenderer(symbol)
f1 = open("d:/test.csv", "r", encoding='utf-8', errors='ignore')
count = 1
for line in f1.readlines():
   rule_based_style(layer, symbol, str(count), line, "red")
   count = count + 1

layer.setRenderer(renderer)
layer.triggerRepaint()
iface.layerTreeView().refreshLayerSymbology(layer.id())

Problem is that my expression which is for example: "Benzinka" = 'ano' AND "typ_silnic" = 'trunk' AND "Corine" = '121' now gets another quotation marks and the result is: """Benzinka"" = 'ano' AND ""typ_silnic"" = 'trunk' AND ""Corine"" = '121'"

it would be good to provide an example of your table structure and content — eurojam, Feb 12 '20 at 09:30
Sorry, my mistake. Each row is one expression which is relate to my dataset.
for example one row: "Benzinka" = 'ano' AND "typ_silnic" = 'trunk' AND "Corine" = '121' — LenkaT, Feb 12 '20 at 09:34
So, you would your rules read like "row1 @excel", "row2 @excel" etc? — Erik, Feb 12 '20 at 09:41
Yeah! I am totaly beginner to using own script in QGIS, I just work with Processing Modeller. — LenkaT, Feb 12 '20 at 09:47
Please use the [edit] button beneath your question to revise it with any requested clarifications. — PolyGeo, Feb 12 '20 at 10:16

score 3 · Answer 1 · answered Feb 12 '20 at 09:58

A basic script like the one below would do the job (based on the solution posted here Adding new rule by using QgsRuleBasedRenderer to existing one in PyQGIS?). The csv file in the example below is d:/test.csv:

def rule_based_style(layer, symbol, label, expression, color):
    root_rule = renderer.rootRule()
    rule = root_rule.children()[0].clone()
    rule.setLabel(label)
    rule.setFilterExpression(expression)
    rule.symbol().setColor(QColor(color))
    root_rule.appendChild(rule)

layer = iface.activeLayer() 
symbol = QgsSymbol.defaultSymbol(layer.geometryType())
renderer = QgsRuleBasedRenderer(symbol)
f1 = open("d:/test.csv", "r", encoding='utf-8', errors='ignore')
count = 1
for line in f1.readlines():
   rule_based_style(layer, symbol, str(count), line, "red")
   count = count + 1

layer.setRenderer(renderer)
layer.triggerRepaint()
iface.layerTreeView().refreshLayerSymbology(layer.id())

It works, but problem is, that each rule has added quotation marks there:
"""Benzinka"" = 'ano' AND ""typ_silnic"" = 'trunk' AND ""Corine"" = '121'" — LenkaT, Feb 12 '20 at 10:12
in my testdata it worked...the data was like: "fclass" = 'farm' "fclass" = 'town' "fclass" = 'town' and "population" > 10000 — eurojam, Feb 12 '20 at 10:27

Rule-based symbology based on given table

1 Answers1