Error when trying to transform ee.Image to vector with Python

Question

I am trying to transform some weather ee.Image to vector format. For context, my final goal is to export data as shapefile, read into GeoPandas and use it as input to a deep learning model, so there may be easier ways to do this since I am pretty noob with gee.

# load the image collection and filter
collection_idx = "JAXA/GPM_L3/GSMaP/v6/operational"
collection = ee.ImageCollection(collection_idx)\
  .filter(ee.Filter.date('2020-01-01', '2020-01-02'))\
  .select("hourlyPrecipRate")

# define amazon region
region = ee.Geometry.Rectangle(
      [
          [-73.99097222, -18.04176667], [-43.95182736,   5.272225]
      ]
  )


# sum hourly values
reduced_quarter_image = collection.reduce(ee.Reducer.sum()).clip(region)

# reduce to vectors using 3 km scale
vector = reduced_quarter_image.gt(0).reduceToVectors({
  "reducer": ee.Reducer.sum(),
  "geometry": region,
  "scale": 3e3,
  "geometryType": 'polygon',
  "crs": reduced_quarter_image.projection()
})

I am receveing the following error:

EEException: Invalid argument for ee.Reducer(): ({'reducer': <ee.Reducer...

What is wrong here?

Daniel Wiell · Accepted Answer · 2023-10-23 11:07:36Z

The JavaScript and Python APIs in EE are very similar, but here is one place where they differ a bit. Almost everywhere, the JavaScript API allow you to provide a single object as argument, just like you tried to do in reduceToVectors(). That's a quite convenient way to emulate named arguments, which JavaScript doesn't support. In Python, however, there are real named argument, so there is no need for this workaround. That's why the Python API does not allow you to provide a dictionary.

You have two simple options to fix this. You either use real named arguments:

vector = reduced_quarter_image.gt(0).reduceToVectors(
  reducer=ee.Reducer.sum(),
  geometry=region,
  scale=3e3,
  geometryType='polygon',
  crs=reduced_quarter_image.projection()
)

Or you convert the dictionary to arguments by simply prepending it with **:

vector = reduced_quarter_image.gt(0).reduceToVectors(**{
  "reducer": ee.Reducer.sum(),
  "geometry": region,
  "scale": 3e3,
  "geometryType": 'polygon',
  "crs": reduced_quarter_image.projection()
})

Thank you! That's what happens when you just copy paste code from documentation example hahah — Giovanni Amorim
– Giovanni Amorim, Commented Oct 24, 2023 at 12:07

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