title: Python/Pandas: Length of a .csv file exported from a dataframe is different from the length of the dataframe
body: <p>I have imported a <code>.csv</code> file using <code>df=pandas.read_csv(.....)</code>. I calculated the number of rows in this dataframe <code>df</code> using <code>print(len(df))</code> and it's size had some 30 rows less than the originally imported file. BUT, when I exported <code>df</code> directly after import as <code>.csv</code> (without doing any operation on this dataframe <code>df</code>) using <code>df.to_csv(....)</code>, then the exported file had the same number of rows as the originally imported <code>.csv</code> file.</p>
  
  <p>It's very hard for me to debug so as to explain the diffference between the lengths of the dataframe on one hand and both imported and exported .csv file on the other, as there are more than half-a-million rows in the dataset. Can anyone provide some hints as to what can cause such a bizzare behavior? </p>