Looking for sample python code (for PythonCaller transformer) that can iterate through various parts of a feature geometry and process part's coordinates.

Iterating over the parts in Python is fairly easy, but modifying the coordinates on all the parts in Python can be surprisingly complicated depending on on the complexity of the features. You'd basically need to deconstruct and rebuild all the geometry parts, with all their specific methods.

Are you 100% sure that you cannot achieve your goal using transformers such as the AffineWarper or the Affiner?

On a side note: some years ago I requested something like a coordinate iterator with a custom callback in the fmepython libraries, but I do not think this was ever implemented. That would have made this fairly easy.

Thank you for the suggestion of Affiner and AffineWarper. I might need them as my work need to find the closest line segment which is parallel to a line through a given point and angle.

(Here ESRI dimension is being exploded as text, lines and points. Special variant of dimensions has underline for the dimension text. In the image you see rectangles around the text. The line at the bottom side of the text will be taken as underline.)

Though I had developed few custom Reader/Writer modules for FME very long time ago, my experience with transformers is very limited! Any help will be appreciated.

partFeature = fmeobjects.FMEFeature()
partFeature.setGeometry(feature.getGeometry().getPartAt(0))
coords = partFeature.getAllCoordinates()

Thanks for the suggestion of building a new feature with part geometry. I failed to see that option. So I came up with an alternative coding as follows:

if(partsCount == 2):

      areaPart = feature.getGeometry().getPartAt(0)

      polyline = areaPart.getBoundaryAsCurve()

      point1 = polyline.getPointAt(2)

      point2 = polyline.getPointAt(3)

      (x1,y1,z1) = point1.getXYZ()

      (x2,y2,z2) = point2.getXYZ()

In case it's useful, here is some sample code to iterate over geometry parts in a PythonCaller:

from fmeobjects import *
 
def FeatureHandler(feature):
    # Decompose aggregates / donuts, if necessary
    if feature.getGeometryType() == FME_GEOM_AGGREGATE:
        aggregate_parts = feature.splitAggregate(True)
    elif feature.getGeometryType() == FME_GEOM_DONUT:
        aggregate_parts = feature.getDonutParts()
    else:
        aggregate_parts = [feature,]
    
    for part in aggregate_parts:
        geom_type = part.getGeometryType()
        if geom_type == FME_GEOM_POINT:
            # Handle point geometry
        elif geom_type == FME_GEOM_LINE:
            # Handle line geometry
        elif geom_type == FME_GEOM_POLYGON:
            # Handle polygon geometry
        else:
            raise FMEException('Unsupported geometry type: ' + str(geom_type))

You can easily extend the if/elif block to handle additional geometry types.