title: Converting a dataframe column to float
body: <p>I have a dataframes called <code>historic_price</code> with two columns called <code>'price'</code> and <code>'item'</code> that I am trying to multiple together storing the result in a different data-frame called <code>dayData</code>, but I get the exception:</p>
  
  <pre><code>TypeError: can't multiply sequence by non-int of type 'float'
  </code></pre>
  
  <p>The <code>'price'</code> column looks like:</p>
  
  <pre><code>           price
  0        5.86500
  1        2.03000
  2       13.55000
  3      639.75450
  4      343.94325
  5     1009.43500
  6      585.60600
  7     2208.72400
  8      807.54800
  9      236.51530
  10      14.34000
  </code></pre>
  
  <p>The <code>'item'</code> column looks like: </p>
  
  <pre><code>     item
  0     0.0
  1     0.0
  2     0.0
  3     0.0
  4     0.0
  5     0.0
  6     0.0
  7     0.0
  8     0.0
  9     0.0
  10    0.0
  </code></pre>
  
  <p>(I know all of the values are zero but even so when I multiple price by item I shoud still get a result (0))</p>
  
  <p>the data types for the two columns are both <code>&lt;class 'pandas.core.series.Series'&gt;</code>  </p>
  
  <p>I am trying to add the product of item and price to the <code>dayData</code> dataframe as follows:</p>
  
  <pre><code>dayData["cash"]  =  historicPrice["price"]  * historicPrice["item"]
  </code></pre>
  
  <p>but I get the exception above.</p>
  
  <p>I have tried converting the columns to float:</p>
  
  <pre><code>dayData["cash"]  =  float(historicPrice["price"])  * float(historicPrice["item"])
  </code></pre>
  
  <p>but with no luck (I get the exception: <code>TypeError: cannot convert the series to &lt;class 'float'&gt;</code>)</p>
  
  <p>Can anyone let me know what i need to do to fix please?</p>
  
  <p>Many thanks</p>