Subscription
0
Best Sellers
New Releases
Books
Videos
Audiobooks
Learning Hub
Free Learning

Product type Book
Published in Dec 2015
Publisher Packt
ISBN-13 9781783551712
Pages 442 pages
Edition 1st Edition
Languages
Concepts
Author (1):
Mr. Fabrizio Romano

Learning Python
Credits
Acknowledgements
www.PacktPub.com
Preface
1. Introduction and First Steps – Take a Deep Breath 2. Built-in Data Types 3. Iterating and Making Decisions 4. Functions, the Building Blocks of Code 5. Saving Time and Memory 6. Advanced Concepts – OOP, Decorators, and Iterators 7. Testing, Profiling, and Dealing with Exceptions 8. The Edges – GUIs and Scripts 9. Data Science 10. Web Development Done Right 11. Debugging and Troubleshooting 12. Summing Up – A Complete Example Index

## Mapping types – dictionaries

Of all the built-in Python data types, the dictionary is probably the most interesting one. It's the only standard mapping type, and it is the backbone of every Python object.

A dictionary maps keys to values. Keys need to be hashable objects, while values can be of any arbitrary type. Dictionaries are mutable objects.

There are quite a few different ways to create a dictionary, so let me give you a simple example of how to create a dictionary equal to `{'A': 1, 'Z': -1}` in five different ways:

```>>> a = dict(A=1, Z=-1)
>>> b = {'A': 1, 'Z': -1}
>>> c = dict(zip(['A', 'Z'], [1, -1]))
>>> d = dict([('A', 1), ('Z', -1)])
>>> e = dict({'Z': -1, 'A': 1})
>>> a == b == c == d == e  # are they all the same?
True  # indeed!
```

Have you noticed those double equals? Assignment is done with one equal, while to check whether an object is the same as another one (or 5 in one go, in this case), we use double equals. There is also...

The rest of the chapter is locked
Register for a free Packt account to unlock a world of extra content!
A free Packt account unlocks extra newsletters, articles, discounted offers, and much more. Start advancing your knowledge today.
Unlock this book and the full library FREE for 7 days
Get unlimited access to 7000+ expert-authored eBooks and videos courses covering every tech area you can think of
Renews at \$19.99/month. Cancel anytime