Extracting data from earthengine object in colab notebook (Python)

Question

I'm using Earth Engine with the Python API in colab, reducing Landsat NDVI over a ROI. I run the following:

imagereduce = image.reduceRegion(**{
    'reducer': ee.Reducer.mean(),
    'geometry': feature,
    'crs': 'EPSG:4326',
    'scale': 30,
    'maxPixels': 1e9
 })

And it give a dictionary object. I can do imagereduce.get('nd') to make it a computed object, but I can't extract the actual value. What I've tried:

• imagereduce.get('nd').getInfo() processes endlessly with no result or exceeds user memory (same if I make it a number or string object)
• imagereduce.evaluate() as shown here gives "Dictionary has no attribute evaluate"
• print(imagereduce.serialize()) gives the metadata for the dictionary
• doing the same process in javascript will give the value in the console, and will allow both .getInfo() and .evaluate to work, but I will need to (a) do this in python and (b) add the value to an array as I go

Any thoughts on how to get the server-side computed object to a client-side value?

Answer 1

The first suggestion appears to be correct, but as you noted exceeds the memory limit. If run with a larger scale it will print out results as I have shown with this simple example below

region = ee.Feature(ee.FeatureCollection('EPA/Ecoregions/2013/L3').filter(ee.Filter.eq('us_l3name', 'Sierra Nevada')).first()).geometry()
image = ee.ImageCollection("LANDSAT/LC08/C01/T1").filterBounds(region).first()


#note I have changed the scale
imagereduce = image.reduceRegion(**{
    'reducer': ee.Reducer.mean(),
    'geometry': region,
    'crs': 'EPSG:4326',
    'scale': 200,
    'maxPixels': 1e9
 })


print(imagereduce.get('B1').getInfo())

"There are multiple options to get past these errors: increase maxPixels, increase the scale, or set bestEffort to true, which automatically computes a new (larger) scale such that maxPixels is not exceeded. If you do not specify maxPixels, the default value is used." https://developers.google.com/earth-engine/guides/reducers_reduce_region