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Modular Programming with Python

You're reading from   Modular Programming with Python Introducing modular techniques for building sophisticated programs using Python

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Product type Paperback
Published in May 2016
Publisher Packt
ISBN-13 9781785884481
Length 246 pages
Edition 1st Edition
Languages
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Author (1):
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Erik Westra Erik Westra
Author Profile Icon Erik Westra
Erik Westra
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Toc

Table of Contents (11) Chapters Close

Preface 1. Introducing Modular Programming 2. Writing Your First Modular Program FREE CHAPTER 3. Using Modules and Packages 4. Using Modules for Real-World Programming 5. Working with Module Patterns 6. Creating Reusable Modules 7. Advanced Module Techniques 8. Testing and Deploying Modules 9. Modular Programming as a Foundation for Good Programming Technique Index

Optional imports


Try opening the Python interactive interpreter and entering the following command:

import nonexistent_module

The interpreter will return the following error message:

ImportError: No module named 'nonexistent_module'

This shouldn't be a surprise to you; you may have even seen this error in your own programs if you made a typo within an import statement.

The interesting thing about this error is that it doesn't just apply where you've made a typo. You can also use this to test if a module or package is available on this particular computer, for example:

try:
    import numpy
    has_numpy = True
except ImportError:
    has_numpy = False

You can then use this to have your program take advantage of the module if it is present, or do something else if the module or package isn't available, like this:

if has_numpy:
    array = numpy.zeros((num_rows, num_cols), dtype=numpy.int32)
else:
    array = []
    for row in num_rows:
        array.append([])

In this example, we check to see if...

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