ee.Dictionary.map

Page Summary

• Dictionary.map applies an algorithm to each key-value pair in a dictionary.

• The algorithm takes a key and its corresponding value as arguments and returns a new value for that key.

• If the algorithm returns null for a key, that key is removed from the resulting dictionary.

Map an algorithm over a dictionary. The algorithm is expected to take 2 arguments, a key from the existing dictionary and the value it corresponds to, and return a new value for the given key. If the algorithm returns null, the key is dropped.

Usage	Returns
Dictionary.map(baseAlgorithm)	Dictionary

Argument	Type	Details
this: dictionary	Dictionary
baseAlgorithm	Algorithm

Examples

Code Editor (JavaScript)

// A dictionary (e.g. results of ee.Image.reduceRegion of an S2 image).
var dict = ee.Dictionary({
  B1: 182,
  B2: 219,
  B3: 443
});

/**
 * Convert S2 surface reflectance units to native scale.
 */
function scale(key, value) {
  return ee.Number(value).divide(1e4);
}

print('S2 surface reflectance in native units', dict.map(scale));

Python setup

See the Python Environment page for information on the Python API and using geemap for interactive development.

import ee
import geemap.core as geemap

Colab (Python)

# A dictionary (e.g. results of ee.Image.reduceRegion of an S2 image).
dic = ee.Dictionary({
    'B1': 182,
    'B2': 219,
    'B3': 443
})


def scale(key, value):
  """Convert S2 surface reflectance units to native scale."""
  return ee.Number(value).divide(1e4)

display('S2 surface reflectance in native units:', dic.map(scale))