Iterate through a list of polygons' centroids in QGIS

Question

I try to calculate the azimuth between a row of polygonsheets to print the number of the last and the next sheet inside the sheet in direction of the last and the next sheet. This should help to orient inside a big Project- Atlas with many sheets. The script (not complete):

for feature in layer.getFeatures(): 
    count = layer.featureCount() 
    geom = feature.geometry()
    polycent = geom.centroid().asPoint()

while i < count
    azimuth = polycent[i].azimuth(polycent[i+1])

The error code is 'float' object has no attribute 'azimuth' - but my polycent[i] is no 'float' object - isn't it? How can I ask for the azimuth between the actual and the next centroid?

Answer 1

In your code, polycent is always set the last polygon's centroid. So you must add centroids to a list.

Change your code into that:

polycents = [] # empty list
for feature in layer.getFeatures():
    geom = feature.geometry()

    # add centroid to the list
    polycents.append(geom.centroid().asPoint())

azimuths = [] 
count = layer.featureCount()
i = 0
while i < count
    azimuth = polycents[i].azimuth(polycents[i+1])
    azimuths.append(azimuth)
    i += 1

# and you can access any azimuth value by index now
print(azimuths[0])