title: Pandas Dataframe: Extract numerical values (including decimals) from string
body: <p>I have a dataframe consisting of a column of strings. I want to extract the numerical numbers of these strings. However, some of the values are in metres, and some in kilometres. How do i detect that there is a "m" or "km" beside the number, standardize the units then extract the numbers to a new column?   </p>
  
  <pre><code>details                 numbers
  Distance                350m
  Longest straight        860m
  Top speed               305km
  Full throttle           61 per cent
  </code></pre>
  
  <p>Desired output:</p>
  
  <pre><code>details                 numbers
  Distance                350
  Longest straight        860
  Top speed               305000
  Full throttle           61
  </code></pre>