title: converting the column of a dataframe into a timestamp
body: <p>I am reading a dataframe into pandas.  It is time series data from an ECG.  I have two columns: the first column is the time the reading is taken, the second column is the value from the ECG.  I am trying to convert the first column into the timestamp and use it as an index.  My code is as follows:</p>
  
  <pre><code>import pandas as pd
  from datetime import datetime
  from datetime import time
  import matplotlib.pyplot as plt
  path='/home/user_1/Documents/heart_data.csv'
  df=pd.read_csv(path)
  df.columns=['Elapsed Time','i']
  df['Elapsed Time']=pd.to_datetime(df['Elapsed Time'], format="'%H:%M.%S%f'") 
  df.set_index('Elapsed Time', inplace=True)
  print(df.head())
  </code></pre>
  
  <p>My problem is that this gives me the output of the column in the form '1900-01-01 00:00:00.000', but I do not want the '1900-01-01' just the time.
  How can I get rid of the date appearing in my column?</p>