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Modern Python Cookbook

You're reading from   Modern Python Cookbook The latest in modern Python recipes for the busy modern programmer

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Product type Paperback
Published in Nov 2016
Publisher Packt
ISBN-13 9781786469250
Length 692 pages
Edition 1st Edition
Languages
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Toc

Table of Contents (12) Chapters Close

Preface 1. Numbers, Strings, and Tuples 2. Statements and Syntax FREE CHAPTER 3. Function Definitions 4. Built-in Data Structures – list, set, dict 5. User Inputs and Outputs 6. Basics of Classes and Objects 7. More Advanced Class Design 8. Input/Output, Physical Format, and Logical Layout 9. Testing 10. Web Services 11. Application Integration

Reversing a copy of a list


Once in a while, we need to reverse the order of the items in a list collection. Some algorithms, for example, produce results in a reversed order. We'll look at the way numbers converted to a specific base are often generated from least-significant to most-significant digit. We generally want to display the values with the most-significant digit first. This leads to a need to reverse the sequence of digits in a list.

We have two ways to reverse a list. First, there's the reverse() method. Then there's this handy trick.

Getting ready

Let's say we're doing a conversion among number bases. We'll look at how a number is represented in a base, and how we can compute that representation from a number.

Any value, v, can be defined as a polynomial function of the various digits, dn, in a given base, b:

v = dn × bn + dn-1 × bn-1 + dn-2 × bn-2 + ... + d1 × b + d0

A rational number has a finite number of digits. An irrational number would have an infinite series of digits.

For...

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