擅长:python、mysql、java
<p>如果<code>d['@Value']</code>是<code>""</code>,它会附加一个空str</p>
<pre><code>#adds d['@Value'] only if its a empty str
pm10 = [d['@Value'] if d['@Value'] == '' else float(d['@Value']) for d in array if d['@SpeciesCode'] == 'PM10']
</code></pre>
<p>例如:</p>
<pre><code>array = [{'@MeasurementDateGMT': '2017-02-25 00:00:00',
'@SpeciesCode': 'CO',
'@Value': '0.3'},
{'@MeasurementDateGMT': '2017-02-25 01:00:00',
'@SpeciesCode': 'PM10',
'@Value': '0.5'},
{'@MeasurementDateGMT': '2017-02-25 01:00:00',
'@SpeciesCode': 'PM10',
'@Value': ''},
{'@MeasurementDateGMT': '2017-02-25 01:00:00',
'@SpeciesCode': 'PM10',
'@Value': '3.5'}]
pm10 = [d['@Value'] if d['@Value'] == '' else float(d['@Value']) for d in array if '@SpeciesCode' in d.keys() if d['@SpeciesCode'] == 'PM10']
</code></pre>
<p>输出为:</p>
<pre><code>[0.5, '', 3.5]
</code></pre>