title: How to fill up a Pandas dataframe in a more concise manner?
body: <p>I use a few lists to fill up a dataframe. In this example, I have 3 columns (a, b, c) and I need to fill up a dataframe from all combinations of the 3:</p>
  <pre><code>import pandas as pd
  
  df = pd.DataFrame(columns=['a', 'b', 'c'])
  for a in np.linspace(1, 100, 20):
      for b in np.linspace(10, 1000, 10):
          for c in [1,4,9]:
              df = df.append({'a':a, 'b':b, 'c':c}, ignore_index=True)
  </code></pre>
  <p>The above code works but uses as many for loops as the number of columns in the dataframe. Is there a more concise/more pythonic way to fill the dataframe up?</p>