Library for implementing Modified Preorder Tree Traversal with your SQLAlchemy Models and working with trees of Model instances, like django-mptt. Docs http://sqlalchemy-mptt.readthedocs.io/

The nested set model is a particular technique for representing nested sets (also known as trees or hierarchies) in relational databases.

Installing

Install from github:

pip install git+http://github.com/uralbash/sqlalchemy_mptt.git

PyPi:

pip install sqlalchemy_mptt

Source:

pip install -e .

Usage

Add mixin to model

fromsqlalchemyimportColumn, Integer, Booleanfromsqlalchemy.ext.declarativeimportdeclarative_basefromsqlalchemy_mptt.mixinsimportBaseNestedSetsBase=declarative_base()
classTree(Base, BaseNestedSets):
__tablename__="tree"id=Column(Integer, primary_key=True)
visible=Column(Boolean)
def__repr__(self):
return"<Node (%s)>"%self.id

Now you can add, move and delete obj!

Insert node

node=Tree(parent_id=6)
session.add(node)

level Nested sets example
1 1(1)22
_______________|___________________
| | |
2 2(2)5 6(4)11 12(7)21
| ^ ^
3 3(3)4 7(5)8 9(6)10 13(8)16 17(10)20
| |
4 14(9)15 18(11)19
level Insert node with parent_id == 6
1 1(1)24
_______________|_________________
| | |
2 2(2)5 6(4)13 14(7)23
| ____|____ ___|____
| | | | |
3 3(3)4 7(5)8 9(6)12 15(8)18 19(10)22
| | |
4 10(23)11 16(9)17 20(11)21

Delete node

node=session.query(Tree).filter(Tree.id==4).one()
session.delete(node)

level Nested sets example
1 1(1)22
_______________|___________________
| | |
2 2(2)5 6(4)11 12(7)21
| ^ ^
3 3(3)4 7(5)8 9(6)10 13(8)16 17(10)20
| |
4 14(9)15 18(11)19
level Delete node == 4
1 1(1)16
_______________|_____
| |
2 2(2)5 6(7)15
| ^
3 3(3)4 7(8)10 11(10)14
| |
4 8(9)9 12(11)13

Update node

node=session.query(Tree).filter(Tree.id==8).one()
node.parent_id=5session.add(node)

level Nested sets example
1 1(1)22
_______________|___________________
| | |
2 2(2)5 6(4)11 12(7)21
| ^ ^
3 3(3)4 7(5)8 9(6)10 13(8)16 17(10)20
| |
4 14(9)15 18(11)19
level Move 8 - > 5
1 1(1)22
_______________|__________________
| | |
2 2(2)5 6(4)15 16(7)21
| ^ |
3 3(3)4 7(5)12 13(6)14 17(10)20
| |
4 8(8)11 18(11)19
|
5 9(9)10

Move node (support multitree)

Nested sets multitree

Move inside

node=session.query(Tree).filter(Tree.id==4).one()
node.move_inside("15")

 4 -> 15
level Nested sets tree1
1 1(1)16
_______________|_____________________
| |
2 2(2)5 6(7)15
| ^
3 3(3)4 7(8)10 11(10)14
| |
4 8(9)9 12(11)13
level Nested sets tree2
1 1(12)28
________________|_______________________
| | |
2 2(13)5 6(15)17 18(18)27
| ^ ^
3 3(14)4 7(4)12 13(16)14 15(17)16 19(19)22 23(21)26
^ | |
4 8(5)9 10(6)11 20(20)21 24(22)25

Move after

node=session.query(Tree).filter(Tree.id==8).one()
node.move_after("5")

level Nested sets example
1 1(1)22
_______________|___________________
| | |
2 2(2)5 6(4)11 12(7)21
| ^ ^
3 3(3)4 7(5)8 9(6)10 13(8)16 17(10)20
| |
4 14(9)15 18(11)19
level Move 8 after 5
1 1(1)22
_______________|__________________
| | |
2 2(2)5 6(4)15 16(7)21
| ^ |
3 3(3)4 7(5)8 9(8)12 13(6)14 17(10)20
| |
4 10(9)11 18(11)19

Move to top level

node=session.query(Tree).filter(Tree.id==15).one()
node.move_after("1")

level tree_id = 1
1 1(1)22
_______________|___________________
| | |
2 2(2)5 6(4)11 12(7)21
| ^ ^
3 3(3)4 7(5)8 9(6)10 13(8)16 17(10)20
| |
4 14(9)15 18(11)19
level tree_id = 2
1 1(15)6
^
2 2(16)3 4(17)5
level tree_id = 3
1 1(12)16
_______________|
| |
2 2(13)5 6(18)15
| ^
3 3(14)4 7(19)10 11(21)14
| |
4 8(20)9 12(22)13

Support and Development

To report bugs, use the issue tracker.

We welcome any contribution: suggestions, ideas, commits with new futures, bug fixes, refactoring, docs, tests, translations, etc...

If you have any questions:

• Use the Discussion board
• Contact the maintainer via email: fayaz.yusuf.khan@gmail.com
• Contact the author via email: sacrud@uralbash.ru or #sacrud IRC channel

Refer the detailed contribution guide in the docs for more information on setting up the development environment, running tests, and contributing to the project.

License

The project is licensed under the MIT license.