Maintaining order in Dictionaries in Python
Maintaining order in Dictionaries: The regular behaviour of Python dictionaries is such that, the order in which the key-value pairs are declared is not necessarily the order in which they are stored in memory. For example:
Maintaining order in Dictionaries
>>> normalDictionary = {2: 'two', 3: 'three', 1: 'one'}
>>> normalDictionary
{1: 'one', 2: 'two', 3: 'three'}
If you wish to have a dictionary which maintains this order, you can use the OrderedDict class of standard library collections.
>>> import collections
>>> orderedDictionary = collections.OrderedDict({2: 'two', 3: 'three', 1: 'one'})
>>> orderedDictionary
OrderedDict([(1, 'one'), (2, 'two'), (3, 'three')])
>>> dict(orderedDictionary)
{1: 'one', 2: 'two', 3: 'three'}
This class was introduced in version 2.7. If you want similar functionality in older versions, I suggest you look at this page.
See also:
- Python 101
- Object Oriented Python
- Design Patterns in Python
- 50+ Handy Standard Library Modules
- 60+ Handy Third Library Modules
- 50+ Tips & Tricks for Python Developers
- 50+ Know-How(s) Every Pythonista Must Know