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Emulating Containers

Let’s see how to use container emulation methods in eemont!

Before anything, let’s import our modules and authenticate in Google Earth Engine:

import ee, eemont

ee.Authenticate()
ee.Initialize()

Now, we are ready to go!

Overview

The eemont package extends the ee.Image, ee.ImageCollection, ee.Feature, ee.FeatureCollection, ee.List and ee.Dictionary classes with container emulation methods.

ee.Image

The following table shows the list of container emulation methods that are overloaded:

Container emulation methods.
Operation	GEE Python method	Container Emulation Method
Get Item By Key	Image.select(bands)	Image[bands]
Get Item By Index	Image.select(index)	Image[index]
Get Item By Slice	Image.slice(start,stop)	Image[start:stop]

ee.ImageCollection

The following table shows the list of container emulation methods that are overloaded:

Container emulation methods.
Operation	GEE Python method	Container Emulation Method
Get Item By Key	ImageCollection.select(bands)	ImageCollection[bands]
Get Item By Index	ImageCollection.select(index)	ImageCollection[index]
Get Item By Slice	ImageCollection.map(lambda x: x.slice(start,stop))	ImageCollection[start:stop]
Length	ImageCollection.size().getInfo()	len(ImageCollection)

ee.Feature

The following table shows the list of container emulation methods that are overloaded:

Container emulation methods.
Operation	GEE Python method	Container Emulation Method
Get Item By Key	Feature.select(properties)	Feature[properties]

ee.FeatureCollection

The following table shows the list of container emulation methods that are overloaded:

Container emulation methods.
Operation	GEE Python method	Container Emulation Method
Get Item By Key	FeatureCollection.select(properties)	FeatureCollection[properties]
Length	FeatureCollection.size().getInfo()	len(FeatureCollection)

ee.List

The following table shows the list of container emulation methods that are overloaded:

Container emulation methods.
Operation	GEE Python method	Container Emulation Method
Get Item By Index	List.select(index)	List[index]
Get Item By Slice	List.slice(start,stop)	List[start:stop]
Length	List.length().getInfo()	len(List)
Contains	List.contains(value).getInfo()	value in List

ee.Dictionary

The following table shows the list of container emulation methods that are overloaded:

Container emulation methods.
Operation	GEE Python method	Container Emulation Method
Get Item By Key	Dictionary.get(key)	Dictionary[key]
Contains	Dictionary.contains(key).getInfo()	key in Dictionary

Usage

Container emulation methods can be used on any of the Earth Engine objects mentioned above. Let’s see how to use them!

Raster Types

Let’s take the Sentinel-2 SR image collection as example:

point = ee.Geometry.Point([-76.0269,2.92846])
S2 = (ee.ImageCollection('COPERNICUS/S2_SR')
   .filterBounds(point)
   .sort('CLOUDY_PIXEL_PERCENTAGE')
   .first()
   .maskClouds()
   .scale())

Now, if we want to select a specific band, we can do it as follows:

NIR = S2['B8']

Or multiple bands:

NIRRED = S2[['B8','B4']]

We can also use regex!:

bands = S2['B.*']

Or an index:

BLUE = S2[1]

Or even better, a slice:

RGB = S2[1:4]

All of these methods can also be done for ee.ImageCollection objects:

S2 = ee.ImageCollection('COPERNICUS/S2_SR').filterBounds(point)['B.*']

And, additionally, we can check the size of the image collection by using len():

len(S2)

Vector Types

Let’s see another example, but using features:

WDPA = ee.FeatureCollection("WCMC/WDPA/current/polygons")

And now, let’s take some properties:

WDPA = WDPA[['WDPAID','NAME','REP_AREA']]

Now, let’s check the size of the feature collection:

len(WDPA)

For the ee.List objects, we can also use container emulaion methods!

Lists

l = ee.List([100,120,230,310,450])

You can get an item by using its index:

l[0]

Or multiple items by using an slice:

l[1:4]

You can also check if an item is in the list:

370 in l

And get the length of the list:

len(l)

Dictionaries

Things work in a similar way for ee.Dictionary classes:

d = ee.Dictionary({'ID': 1,'Name': 'Natural Park','Area': 3240})

We can get a value by using its key:

d['Name']

We can also check if a key is in a dictionary:

'Area' in d

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Histogram Matching