Other Options

To insert or update (upsert) a record using an external ID, use:

sf.Contact.upsert('customExtIdField__c/11999',{'LastName': 'Smith','Email': 'smith@example.com'})

To format an external ID that could contain non-URL-safe characters, use:

external_id = format_external_id('customExtIdField__c', 'this/that & the other')

To retrieve basic metadata use:

sf.Contact.metadata()

To retrieve a description of the object, use:

sf.Contact.describe()

To retrieve a description of the record layout of an object by its record layout unique id, use:

sf.Contact.describe_layout('39wmxcw9r23r492')

To retrieve a list of top level description of instance metadata, user:

sf.describe()

for x in sf.describe()["sobjects"]:
  print x["label"]