ee.ImageCollection.getNumber

// A contrived, empty image collection for simple demonstration.
var col = ee.ImageCollection([]);
print('Collection without properties', col);

// Set collection properties using a dictionary.
col = col.set({
  project_name: 'biomass_tracking',
  project_id: 3,
  plot_ids: ee.Array([7, 11, 20])
});

// Set collection properties using a series of key-value pairs.
col = col.set('project_year', 2018,
              'rgb_vis', 'false_color');

print('Collection with properties', col);

// Get a dictionary of collection property keys and values.
print('Property keys and values (ee.Dictionary)', col.toDictionary());

// Get the value of a collection property. To use the result of
// ee.ImageCollection.get in further computation, you need to cast it to the
// appropriate class, for example, ee.Number(result) or ee.String(result).
print('Project ID (ambiguous object)', col.get('project_id'));

// Get the value of a string collection property as an ee.String object.
print('Project name (ee.String)', col.getString('project_name'));

// Get the value of a numeric collection property as an ee.Number object.
print('Project year (ee.Number)', col.getNumber('project_year'));

// Get the value of an ee.Array collection property as an ee.Array object.
print('Plot IDs (ee.Array)', col.getArray('plot_ids'));

from pprint import pprint

# A contrived, empty image collection for simple demonstration.
col = ee.ImageCollection([])
print('Collection without properties:')
pprint(col.getInfo())

# Set collection properties using a dictionary.
col = col.set({
    'project_name': 'biomass_tracking',
    'project_id': 3,
    'plot_ids': ee.Array([7, 11, 20])
})

# Set collection properties using a series of key-value pairs.
col = col.set('project_year', 2018,
              'rgb_vis', 'false_color')

print('Collection with properties:')
pprint(col.getInfo())

# Get a dictionary of collection property keys and values.
print('Property keys and values (ee.Dictionary):')
pprint(col.toDictionary().getInfo())

# Get the value of a collection property. To use the result of
# ee.ImageCollection.get in further computation, you need to cast it to the
# appropriate class, for example, ee.Number(result) or ee.String(result).
print('Project ID (ambiguous object):', col.get('project_id').getInfo())

# Get the value of a string collection property as an ee.String object.
print('Project name (ee.String):', col.getString('project_name').getInfo())

# Get the value of a numeric collection property as an ee.Number object.
print('Project year (ee.Number):', col.getNumber('project_year').getInfo())

# Get the value of an ee.Array collection property as an ee.Array object.
print('Plot IDs (ee.Array):', col.getArray('plot_ids').getInfo())