Pandas read_table use first column as index

Question

I have a little bit of a problem here. I have a txt file containing lines of the form (let's say for line 1):

id1-a1-b1-c1

I want to load it in a data frame using pandas with the index being the id's and the columns name being 'A', 'B', 'C' and the values the corresponding ai, bi, ci

at the end I want the dataframe to look like:

    'A'   'B'  'C'
id1  a1    b1   c1
id2  a2    b2   c2
...   ...   ...  ...

I may want to read by chunks in the file is large but let's assume I read at once:

with open('file.txt') as f:
    table = pd.read_table(f, sep='-', index_col=0, header=None,   lineterminator='\n')

and rename the columns

table.columns = ['A','B','C']

my current output is something like:

    'A'   'B'  'C'
0
id1  a1    b1   c1
id2  a2    b2   c2
...   ...   ...  ...

there is an extra row that I can't explain

Thanks

EDIT

when I try to add the field

chunksize=20

and after doing:

for chunk in table:
    print(chunk)

I get the following error:

pandas.parser.CParserError: Error tokenizing data. C error: Calling read(nbytes) on source failed. Try engine='python'.

Answer 1

If you know the column names before the file is read, pass the list using names parameter of read_table:

with open('file.txt') as f:
    table = pd.read_table(f, sep='-', index_col=0, header=None, names=['A','B','C'],
                          lineterminator='\n')

Which outputs:

      A   B   C
id1  a1  b1  c1
id2  a2  b2  c2