additional column when saving pandas data frame to csv file
<p>Here the the code to process and save csv file, and raw input csv file and output csv file, using pandas on Python 2.7 and wondering why there is an additional column at the beginning when saving the file? Thanks.</p>

<pre><code>c_a,c_b,c_c,c_d
hello,python,pandas,0.0
hi,java,pandas,1.0
ho,c++,numpy,0.0

sample = pd.read_csv('123.csv', header=None, skiprows=1,
    dtype={0:str, 1:str, 2:str, 3:float})
sample.columns = pd.Index(data=['c_a', 'c_b', 'c_c', 'c_d'])
sample['c_d'] = sample['c_d'].astype('int64')
sample.to_csv('saved.csv')
</code></pre>

<p>Here is the saved file, there is an additional column at the beginning, whose values are <code>0, 1, 2</code>.</p>

<pre><code>cat saved.csv
,c_a,c_b,c_c,c_d
0,hello,python,pandas,0
1,hi,java,pandas,1
2,ho,c++,numpy,0
</code></pre>