2

I am trying to perform a if/elif/else routine in the field calculator environment from PyQGIS (i.e. coding in Python).

My code is the following, however I keep getting indentation errors. The field calculator code is working fine for normal operations between fields, but I am not managing to get the conditional statement working.

Note that I get the error already when defining the function funct_calculator with the conditonal statements, so before actually calculating attributes.

myField = QgsField( 'wg_maize', QVariant.Double )
voronoi_clipped_reprojected.dataProvider().addAttributes([myField])
voronoi_clipped_reprojected.updateFields()

def funct_calculator():
    if feature['clzonemaj'] = 5401:
        feature['maize_area'] * wr_rainfed_maize_5401
    elif feature['clzonemaj'] = 6401:
        feature['maize_area'] * wr_rainfed_maize_6401
    elif feature['clzonemaj'] = 7101:
        feature['maize_area'] * wr_rainfed_maize_7101
    elif feature['clzonemaj'] = 7501:
        feature['maize_area'] * wr_rainfed_maize_7501
    elif feature['clzonemaj'] = 7701:
        feature['maize_area'] * wr_rainfed_maize_7701
    else:
        0

def calculate_attributes():
    with edit(voronoi_clipped_reprojected):
        for feature in voronoi_clipped_reprojected.getFeatures():
            feature.setAttribute(feature.fieldNameIndex('wg_maize'), funct_calculator)
            voronoi_clipped_reprojected.updateFeature(feature)
    print(f"Attribute calculated")

calculate_attributes()

In particular, I get the following error:

def funct_calculator():
    if feature['clzonemaj'] = 5401:
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 2
    if feature['clzonemaj'] = 5401:
                            ^
SyntaxError: invalid syntax
        feature['maize_area'] * wr_rainfed_maize_5401
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 1
    feature['maize_area'] * wr_rainfed_maize_5401
    ^
IndentationError: unexpected indent
    elif feature['clzonemaj'] = 6401:
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 1
    elif feature['clzonemaj'] = 6401:
    ^
IndentationError: unexpected indent
        feature['maize_area'] * wr_rainfed_maize_6401
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 1
    feature['maize_area'] * wr_rainfed_maize_6401
    ^
IndentationError: unexpected indent
    elif feature['clzonemaj'] = 7101:
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 1
    elif feature['clzonemaj'] = 7101:
    ^
IndentationError: unexpected indent
        feature['maize_area'] * wr_rainfed_maize_7101
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 1
    feature['maize_area'] * wr_rainfed_maize_7101
    ^
IndentationError: unexpected indent
    elif feature['clzonemaj'] = 7501:
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 1
    elif feature['clzonemaj'] = 7501:
    ^
IndentationError: unexpected indent
        feature['maize_area'] * wr_rainfed_maize_7501
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 1
    feature['maize_area'] * wr_rainfed_maize_7501
    ^
IndentationError: unexpected indent
    elif feature['clzonemaj'] = 7701:
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 1
    elif feature['clzonemaj'] = 7701:
    ^
IndentationError: unexpected indent
        feature['maize_area'] * wr_rainfed_maize_7701
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 1
    feature['maize_area'] * wr_rainfed_maize_7701
    ^
IndentationError: unexpected indent
    else:
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 1
    else:
    ^
IndentationError: unexpected indent
        0
Traceback (most recent call last):
  File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 168, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 99, in _maybe_compile
    raise err1
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 87, in _maybe_compile
    code1 = compiler(source + "\n", filename, symbol)
  File "C:\OSGEO4~1\apps\Python37\lib\codeop.py", line 133, in __call__
    codeob = compile(source, filename, symbol, self.flags, 1)
  File "<input>", line 1
    0
    ^
IndentationError: unexpected indent
  • 1
    You should use == to make comparisons in the if clause. For example: if feature['clzonemaj'] == 5401: – Leo Cardona Jun 12 at 13:25
  • 1
    Solution was easy and silly. Thank you very much! If you reply properly I will mark it as solved. – Jackk Jun 12 at 13:43
2

Everything is fine, you just have to use the == to make comparisons in the if clause.

myField = QgsField( 'wg_maize', QVariant.Double )
voronoi_clipped_reprojected.dataProvider().addAttributes([myField])
voronoi_clipped_reprojected.updateFields()

def funct_calculator():
    if feature['clzonemaj'] == 5401:
        feature['maize_area'] * wr_rainfed_maize_5401
    elif feature['clzonemaj'] == 6401:
        feature['maize_area'] * wr_rainfed_maize_6401
    elif feature['clzonemaj'] == 7101:
        feature['maize_area'] * wr_rainfed_maize_7101
    elif feature['clzonemaj'] == 7501:
        feature['maize_area'] * wr_rainfed_maize_7501
    elif feature['clzonemaj'] == 7701:
        feature['maize_area'] * wr_rainfed_maize_7701
    else:
        0

def calculate_attributes():
    with edit(voronoi_clipped_reprojected):
        for feature in voronoi_clipped_reprojected.getFeatures():
            feature.setAttribute(feature.fieldNameIndex('wg_maize'), funct_calculator)
            voronoi_clipped_reprojected.updateFeature(feature)
    print(f"Attribute calculated")

calculate_attributes()

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