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Modern Python Cookbook

You're reading from   Modern Python Cookbook 133 recipes to develop flawless and expressive programs in Python 3.8

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Product type Paperback
Published in Jul 2020
Publisher Packt
ISBN-13 9781800207455
Length 822 pages
Edition 2nd Edition
Languages
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Author (1):
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Steven F. Lott Steven F. Lott
Author Profile Icon Steven F. Lott
Steven F. Lott
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Toc

Table of Contents (18) Chapters Close

Preface 1. Numbers, Strings, and Tuples 2. Statements and Syntax FREE CHAPTER 3. Function Definitions 4. Built-In Data Structures Part 1: Lists and Sets 5. Built-In Data Structures Part 2: Dictionaries 6. User Inputs and Outputs 7. Basics of Classes and Objects 8. More Advanced Class Design 9. Functional Programming Features 10. Input/Output, Physical Format, and Logical Layout 11. Testing 12. Web Services 13. Application Integration: Configuration 14. Application Integration: Combination 15. Statistical Programming and Linear Regression 16. Other Books You May Enjoy
17. Index

Making shallow and deep copies of objects

Throughout this chapter, we've talked about how assignment statements share references to objects. Objects are not normally copied. When we write:

a = b

we now have two references to the same underlying object. If the object of b has a mutable type, like the list, set, or dict types, then both a and b are references to the same mutable object.

As we saw in the Understanding variables, references, and assignment recipe, a change to the a variable changes the list object that both a and b refer to.

Most of the time, this is the behavior we want. There are rare situations in which we want to actually have two independent objects created from one original object.

There are two ways to break the connection that exists when two variables are references to the same underlying object:

  • Making a shallow copy of the structure
  • Making a deep copy of the structure

Getting ready

Python does...

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