Fields

$set

Replaces the value of a field with the specified value.

col.insert({"item": {"amount": 100}})
col.update({"$set": {"item.amount": 200, "item.name": "Item 1"}})
col.list() # [{"item": {"amount": 200, "name": "Item 1"}}]

$unset

Deletes a particular field.

col.insert({"item": {"amount": 100, "name": "Item 1"}})
col.update({"$unset": {"item.amount": True}})
col.list()  # [{"item": {"name": "Item 1"}}]
col.update({"$unset": {"item.name": False}})
col.list()  # [{"item": {"name": "Item 1"}}]

$inc

Increments a field by a specified value.

col.insert({"item": {"amount": 100}})
col.update({"$inc": {"item.amount": 20}})
col.list() # [{"item": {"amount": 120}}]

$map

Replaces the value of the specified field with the function return value. It takes the old value and returns the new one. If the specified field doesn’t exist, it will take petdb.NON_EXISTENT object.

col.insert({"item": {"amount": 100}})
col.update({"$map": {"item.amount": lambda val: int(val / 2)}})
col.list() # [{"item": {"amount": 50}}]
col.update({"$map": {"item": lambda item: {"name": "Item 1", "amount": item["amount"]}}})
col.list() # [{"item": {"name": "Item 1", "amount": 50}}]