title: Count number of values in an entire DataFrame
body: <p>I currently have DataFrame with 50 columns and around 50000 rows. I'm trying to find the total amount of times a value (e.g. 2) appears in the entire DataFrame.</p>
  
  <p>The DataFrame only contains values between 0 to 7. I am able to execute the code for a single column using this:</p>
  
  <pre><code>print(df['col1'].value_counts())
  </code></pre>
  
  <p>I then attempted to create a for loop like the one shown below:</p>
  
  <pre><code>for cols in df:
      print(df[cols].value_counts())
  </code></pre>
  
  <p>This works, but it prints it out as individual results for each column.</p>
  
  <p>Instead of having the results split up per column, I'm trying to get something like what's shown below, but for all the columns in the DataFrame combined and not just 1 column.</p>
  
  <pre><code>val    no.
  7.0    165
  3.0    127
  5.0     118
  6.0     112
  2.0      98
  4.0      88
  1.0      64
  0.0      21
  Name: col1, dtype: int64
  </code></pre>
  
  <p>Any help would be greatly appreciated!</p>