擅长:python、mysql、java
<blockquote>
<p>that there are occasional missing values where there is just an empty
string.</p>
</blockquote>
<p>如果我理解正确,以下简单条件应符合您的要求:</p>
<pre><code># the example was slightly modified to show empty strings proccessing
array = [{'@MeasurementDateGMT': '2017-02-25 00:00:00',
'@SpeciesCode': 'PM10',
'@Value': '0.3'},
{'@MeasurementDateGMT': '2017-02-25 01:00:00',
'@SpeciesCode': 'PM10',
'@Value': ''},
{'@MeasurementDateGMT': '2017-02-25 01:00:00',
'@SpeciesCode': 'PM10',
'@Value': '0.5'}]
pm10 = [float(d['@Value']) if d['@Value'].strip() else '' for d in array if d['@SpeciesCode'] == 'PM10']
print(pm10)
</code></pre>
<p>输出:</p>
<pre><code>[0.3, '', 0.5]
</code></pre>