2. Bag

Last page update: November 10, 2011

• introduction
• section index

2.1. introduction

A Bag is a Genro class used to create a multi-purpose datastructure, and it is ideal for storing and retrieving any kind of complex hierarchical data in tidily and deeply way.

Nested elements can be accessed with a path of keys joined with dots:

>>> mybag['foo.bar'] = 'spam'
>>> x = mybag['foo.bar']

A Bag takes some Dictionary features:

• Both Bag and Dictionary are made by a set of key:value pairs.
• Values are accessed using a key (called path).
• Both Bag and Dictionary can shrink or grow as needed.
• Both Bag and Dictionary can be nested.
• A Bag inherit some Dictionary methods [1] and some syntax forms (that we will document in the following Bag documentation pages).

Most important, a Bag carries some features that Dictionary hasn’t got:

Dictionary	Bag
A Dictionary is a mutable unordered set of key:value pairs.	A Bag is a unmutable ordered set of key:value pairs.
A Dictionary is NOT hierarchic.	A Bag IS hierarchic.
A Dictionary is NOT ordered.	A Bag IS ordered.
Keys must be unique.	You can have different values with the same key.

2.2. section index

• 1. Bag definitions
• 2. Basic functions
• 3. Basic functions (part two)
• 4. Attributes
• 5. Nodes
• 6. Advanced functions
• 7. Bag from/to source
• 8. Resolver and dynamic Bags
• 9. Bag library reference

Footnotes:

[1]	Check the Dictionary methods implemented by Bag and other related methods section for further details.

[2]	You might be wondering why we call “label” the key argument of a Bag: its origin is storical: the Bag has been created before Genro Team began to use Python language.