title: extra separator from pandas.to_csv function
body: <p>I have a dataset that I am trying to split into a training and test set. 
  I have made the following script to split the data as aforementioned: </p>
  
  <pre><code>import pandas as pd
  import numpy as np 
  
  data_path = "/path_to_data/"
  
  df = pd.read_csv(data_path+"product.dlm", header=0, delimiter="|")
  ts =  df.shape 
  # print "data dimension", ts
  # print "product attributes \n", train.columns.values 
  
  
  #shuffle data set, and split to train and test set. 
  new_train = df.reindex(np.random.permutation(df.index))
  
  indice_90_percent = int((ts[0]/100.0)* 90)
  
  
  new_train[:indice_90_percent].to_csv('train_products.txt',header=True, sep="|")
  new_train[indice_90_percent:].to_csv('test_products.txt',header=True, sep="|")
  </code></pre>
  
  <p>The original file looks like</p>
  
  <pre><code>label1|label2|...|labeln
  371658|description|...|"some value"
  </code></pre>
  
  <p>the file generated by to_csv()
  has one extra column without a name at the begining, which looks like this </p>
  
  <pre><code>|label1|label2|...|labeln|
  452488|422932|description|...|"some value"|
  </code></pre>
  
  <p>What am I missing? </p>