round_mean.py

from osgeo import ogr

# Open shapefile and count features
source = ogr.Open('building-means.shp', update=True)
layer = source.GetLayer()
features_count = layer.GetFeatureCount()

# Create new field
new_field = ogr.FieldDefn('mean_rnd', ogr.OFTReal) # Define new floating-point field

new_field.SetWidth(10)
new_field.SetPrecision(1) # Enforce precision of one decimal place
layer.CreateField(new_field)

# Loop over all features, rounding value of 'mean' field
features_processed = 0

for feature in layer:
    mean = feature.GetField('mean')

    feature.SetField('mean_rnd', mean) # Copy 'mean' field into new 'mean_rnd' field
    layer.SetFeature(feature)
    
    features_processed += 1 # Update count of features processed

    # Print update on number of features processed to console for progress monitoring
    print('{} of {} features processed'.format(features_processed, features_count))

# Close shapefile when done
source = None