Wiki FAQ: Lambda Functions Update and Formatting

[MarkMoretto]

I wanted to push an update for the FAQ in the Wiki section. I just cleaned up and added a little bit to the section about Lambda notation. Below is the updated replacement.

# syntax error, lambda notation python 2.7 vs 3.x

<style type="text/css">
.container {
  display: inline-grid;
  align-items: center;
  justify-content: center;
}

.cap-map {
    text-align: center;
    font-size: 24px;
    text-decoration: none;
    vertical-align: middle;
}

.header-cell {
  text-align: center;
  font-weight: bold;
  vertical-align: middle;
}

.center-cell {
    text-align: center;
    vertical-align: middle;
}

.function-cell {
    text-align: left;
    font-family: monospace;
    white-space: pre;
    vertical-align: middle;
}
</style>

<div class="container">
    <table>
        <caption class="cap-map">Mapping RDDs with Single Values</caption>
        <thead>
            <tr>
                <th class="header-cell">Python Version</th>
                <th class="header-cell">Solution #</th>
                <th class="header-cell">Lambda Function</th>
            </tr>
        </thead>
        <tbody>
            <tr>
                <td class="center-cell">2.7</td>
                <td class="center-cell">1</td>
                <td class="function-cell">result_array_ts = result_rdd.map(lambda (ts, voltage): ts).collect()</td>
            </tr>
            <tr>
                <td class="center-cell">3.x</td>
                <td class="center-cell">1</td>
                <td class="function-cell">result_array_ts = result_rdd.map(lambda ts_voltage: ts_voltage[0]).collect()</td>
            </tr>
            <tr>
                <td class="center-cell">3.x</td>
                <td class="center-cell">2</td>
                <td class="function-cell">result_array_voltage = result_rdd.map(lambda ts_voltage: ts_voltage[1]).collect()</td>
            </tr>        
        </tbody>
    </table>
    <br />
    <table>
        <caption class="cap-map">Mapping RDDs with Multiple Values</caption>
        <thead>
            <tr>
                <th class="header-cell">Python Version</th>
                <th class="header-cell">Lambda Function</th>
            </tr>
        </thead>
        <tbody>
            <tr>
                <td class="center-cell">2.7</td>
                <td class="function-cell">rdd.map(lambda (x, y): pow(x * y, 2)).sum()</td>
            </tr>
            <tr>
                <td class="center-cell">3.x</td>
                <td class="function-cell">rdd.map(lambda xy: pow(xy[0] * xy[1], 2)).sum()</td>
            </tr>
        </tbody>
    </table>
</div>

The less-fancy versions (HTML and markdown) are:

Mapping RDDs with Multiple Values

Python Version	Solution #	Lambda Function
2.7	1	result_array_ts = result_rdd.map(lambda (ts, voltage): ts).collect()
3.x	1	result_array_ts = result_rdd.map(lambda ts_voltage: ts_voltage[0]).collect()
3.x	2	result_array_voltage = result_rdd.map(lambda ts_voltage: ts_voltage[1]).collect()

Mapping RDDs with Multiple Values

Python Version	Lambda Function
2.7	rdd.map(lambda (x, y): pow(x * y, 2)).sum()
3.x	rdd.map(lambda xy: pow(xy[0] * xy[1], 2)).sum()

Mapping RDDs with Single Values

Python Ver.	Solution #	Lambda Func.
2.7	1	result_array_ts = result_rdd.map(lambda (ts, voltage): ts).collect()
3.x	1	result_array_ts = result_rdd.map(lambda ts_voltage: ts_voltage[0]).collect()
3.x	2	result_array_voltage = result_rdd.map(lambda ts_voltage: ts_voltage[1]).collect()

Mapping RDDs with Multiple Values

Python Ver.	Lambda Func.
2.7	rdd.map(lambda (x, y): pow(x * y, 2)).sum()
3.x	rdd.map(lambda xy: pow(xy[0] * xy[1], 2)).sum()