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Fix prefix argument for read_csv/read_table #5733

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Jan 3, 2014
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Fix prefix argument for read_csv/read_table #5733

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d91dd19
Fix prefix argument for read_csv/read_table
nmichaud Dec 18, 2013
48ee1ec
BUG: add tests for read_table/read_csv `prefix` argument
nmichaud Dec 18, 2013
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4 changes: 2 additions & 2 deletions pandas/io/parsers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -972,7 +972,7 @@ def __init__(self, src, **kwds):

if self.names is None:
if self.prefix:
self.names = ['X%d' % i
self.names = ['%s%d' % (self.prefix, i)
for i in range(self._reader.table_width)]
else:
self.names = lrange(self._reader.table_width)
Expand Down Expand Up @@ -1563,7 +1563,7 @@ def _infer_columns(self):
num_original_columns = ncols
if not names:
if self.prefix:
columns = [['X%d' % i for i in range(ncols)]]
columns = [['%s%d' % (self.prefix,i) for i in range(ncols)]]
else:
columns = [lrange(ncols)]
columns = self._handle_usecols(columns, columns[0])
Expand Down
16 changes: 16 additions & 0 deletions pandas/io/tests/test_parsers.py
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Expand Up @@ -968,6 +968,22 @@ def test_no_header(self):

self.assert_(np.array_equal(df2.columns, names))

def test_no_header_prefix(self):
data = """1,2,3,4,5
6,7,8,9,10
11,12,13,14,15
"""
df_pref = self.read_table(StringIO(data), sep=',', prefix='Field',
header=None)

expected = [[1, 2, 3, 4, 5.],
[6, 7, 8, 9, 10],
[11, 12, 13, 14, 15]]
tm.assert_almost_equal(df_pref.values, expected)

self.assert_(np.array_equal(df_pref.columns,
['Field0', 'Field1', 'Field2', 'Field3', 'Field4']))

def test_header_with_index_col(self):
data = """foo,1,2,3
bar,4,5,6
Expand Down