title: Moving multiple columns of pandas dataframe to csv
body: <p>I have a dataframe that I imported using <code>pandas.read_csv</code> that is two columns. I manipulated one column, and now would like to <code>save</code> all three columns as a <code>.csv</code> file. I have been able to save one column at a time, but am unable to get all three (df.Time, df.Distance, and df.Velocity). Here is what I'm working with.</p>
  
  <pre><code>`import pandas as pd
  
   df=pd.read_csv('/Users/path/file.csv', delimiter=',', usecols=['A', 'B'])
  
   df.columns = ['Time', 'Range']
  
   df.Time = df['Time'].round(14)
   df.Range = df['Range'].round(14)
  
   df.Velocity = (df.Range.shift(1) - df.Range) / (df.Time.shift(1) -df.Time)
  
   df2 = [df.Time, df.Range, df.Velocity]
  
   df2.to_csv('test5.csv', columns = header)` 
  </code></pre>