1.15 Itse1359-1070-strings part 2

Table of contents

• Preface
  • Viewing tip
    • Figures
    • Listings
• Introduction
  • What you have learned
  • What you will learn
  • Indexing
    • A practical example
    • Assigning an ordinal index
    • Using an ordinal index
    • Index values automatically assigned
  • Slicing
• A sample program
  • The program listing
  • Will discuss in fragments
• Interesting code fragments
  • Extract a single character
    • Create a string object to work with
    • Visualizing the string object
    • Index values always begin with zero
    • Display the character at index 3
    • Is this the fourth character?
    • An important and potentially confusing point
    • Not like eggs
  • A simple slice
    • Slice notation
    • The end is non-inclusive
    • Extract the first word in the string
    • Extract the last word in the string
  • A more complicated slice
    • Omitting the first index
    • Omitting the second index
    • Print the entire string
    • Print an empty string
    • Negative indices
    • Eliminating confusion
  • Getting the length of a string
  • The complete output
• A string is Immutable
• Miscellaneous
• Complete program listing

Preface

This module is one in a collection of modules on Python designed for teaching ITSE 1359 Introduction to Scripting Languages: Python at Austin Community College in Austin, TX. It will expand your knowledge of strings, and in additionwill introduce you to some concepts that will be useful with other data types as well: indexing and slicing .

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the Figuresand Listings while you are reading about them.

(Note to blind and visually impaired students: all of the Listings in this module are presented in plain text format and should be accessible using anaudio screen reader or a braille display. However, some of the Figures contain images that may not be accessible.)

Figures

• Figure 1 . Visualizing the string object.

Listings

• Listing 1 . Extract a single character.
• Listing 2 . A simple slice.
• Listing 3 . Omitting the first index.
• Listing 4 . Omitting the second index.
• Listing 5 . Print the entire string.
• Listing 6 . Print an empty string.
• Listing 7 . Negative indices.
• Listing 8 . Getting the length of a string.
• Listing 9 . The script named String01.py.

Introduction

What you have learned

You have learned how to write some simple Python programs and to execute them interactively.

You have learned how to capture simple programs in script files and to execute those script files.

You have learned how to construct programs, including the indentation required by Python.

You have also learned some of the fundamental concepts involving strings.

What you will learn

This module will expand your knowledge of strings and in addition will introduce you to some concepts that will be useful with other data types aswell: indexing and slicing .

Indexing

According to WolframMathWorld , "... an ordinal number is an adjective which describes the numerical position of an object, e.g., first,second, third, etc."