Arrays

$push, $append

Appends a specified value to an array.

col.insert({"item": {"skus": [3, 5, 6, 7, 7, 8]}})
col.update({"$push": {"item.skus": 20}})
col.list() # [{"item": {"skus": [3, 5, 6, 7, 7, 8, 20]}}]

$addToSet

Adds a value to an array unless the value is already present, in which case $addToSet does nothing to that array.

col.insert({"item": {"skus": [3, 5, 6, 7, 7, 8]}})
col.update({"$addToSet": {"item.skus": 20}})
col.update({"$addToSet": {"item.skus": 6}})
col.list() # [{"item": {"skus": [3, 5, 6, 7, 7, 8, 20]}}]

$pull, $remove

Removes from an existing array all instances of a value or values that match a specified condition.

col.insert({"item": {"skus": [3, 5, 6, 7, 7, 8]}})
col.update({"$pull": {"item.skus": {"$gte": 6}}})
col.list() # [{"item": {"skus": [3, 5]}}]
col.update({"$pull": {"item.skus": 3}})
col.list() # [{"item": {"skus": [5]}}]