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copied!<p>You were on the right track using <code>re</code>; your best bet (assuming the decimal can be arbitrary, etc.) is something like this:</p> <pre><code>import re def temp(): command = "/opt/vc/bin/vcgencmd measure_temp" proc = subprocess.Popen(command, stdout=subprocess.PIPE, shell=True) output = proc.stdout.read() # Build the regex. Use () to capture the group; we want any number of # digits \d or decimal points \. that is preceded by temp= and # followed by 'C temp_regex = re.compile(r'temp=([\d\.]*)\'C') matches = re.findall(temp_regex, output) # now matches = ['54.1'] temp = float(matches[0]) return temp </code></pre> <p>The regex captures any combination of numbers and decimal places (e.g. <code>12.34.56</code> would get matched); you could restrict it if necessary to only allow a single decimal place, but that's more work than it appears to be worth, if you can trust that the data you're getting back is well-formed. If you do want the number to be more precise, you could compile the regex like this (for at least one numeral preceding the decimal place and exactly one following it):</p> <pre><code>temp_regex = re.compile(r'temp=(\d+.\d)\'C') </code></pre> <p>Again, we capture the expression using the parentheses (captured groups are <a href="http://docs.python.org/3/library/re.html#re.findall" rel="nofollow">returned</a> by findall), but this time, increase the specificity of what we're looking for. This will capture any number like <code>123.4</code> but not <code>.4</code> and not <code>123.</code> If you find that you need to broaden it out a bit but still want only one decimal place:</p> <pre><code>temp_regex = re.compile(r'temp=(\d+.\d+)\'C') </code></pre> <p>That will capture any number with at least one numeral proceeding and following the decimal, so <code>1234.5678</code> would match but <code>1234.</code> would not and <code>.1234</code> would not.</p> <p>As an alternative to using <code>re.findall()</code>, you might use <code>re.match()</code>, which returns <a href="http://docs.python.org/3/library/re.html#match-objects" rel="nofollow">match objects</a>. Then your usage would look something like this (using the direct method, rather than pre-compiling the string:</p> <pre><code>match = re.match(r'temp=(\d+.\d+)\'C', output) if match: temp = float(match.group(1)) # get the first matching group captured by () else: pass # You should add some error handling here </code></pre> <p>One of the things this makes clearer than the way I had <code>re.findall()</code> above is that if nothing is captured, you have an issue, and you need to figure out how to handle it.</p> <hr> <p>You can look at other ways to vary that up at <a href="http://www.regular-expressions.info/" rel="nofollow">Regular-Expressions.info</a>, easily the best site I've found on the web for a quick resource on the topic.</p>

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