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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 (18) Chapters Close

Title Page
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
1. Numbers, Strings, and Tuples FREE CHAPTER 2. Statements and Syntax 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 Index

Picking a subset - three ways to filter


In the Using stacked generator expressions recipe, we wrote a generator function that excluded some rows from a set of data. We defined a function like this:

    def skip_header_date(rows): 
        for row in rows: 
            if row[0] == 'date': 
                continue 
            yield row 

When the condition is truerow[0] is date—the continue statement will skip the rest of the statements in the body of the for statement. In this case, there's only a single statement, yield row.

There are two conditions:

  • row[0] == 'date': The yield statement is skipped; the row is rejected from further processing

  • row[0] != 'date': The yield statement means that the row will be passed on to the function or statement that's consuming the data

At four lines of code, this seems long-winded. The for...if...yield pattern is clearly boilerplate, and only the condition is really material in this kind of construct.

Can we express this more succinctly...

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