Closed
Description
The following code should return a new Series with a single value, but raises a ValueError:
import pandas as pd
s = pd.Series([100])
pd.concat([s.iloc[::-1]])The corresponding example with a DataFrame also raises a ValueError:
import pandas as pd
df = pd.DataFrame([100])
pd.concat([df.iloc[::-1]])The DataFrame version can be reproduced with multiple columns, but any of the following modifications will prevent the bug:
- create Series or DataFrame with len > 1
- concatenate more than one object
- remove the reversing operation
.iloc[::-1] - pass ignore_index=True to pd.concat
This bug appeared as an edge case in a function that usually handles DataFrames with multiple rows.
Traceback for the Series example
C:\Anaconda3\lib\site-packages\pandas\core\reshape\concat.py in concat(objs, axis, join, ignore_index, keys, levels, names, verify_integrity, sort, copy)
296 )
297
--> 298 return op.get_result()
299
300
C:\Anaconda3\lib\site-packages\pandas\core\reshape\concat.py in get_result(self)
483
484 res = concat_compat(arrs, axis=0)
--> 485 result = cons(res, index=self.new_axes[0], name=name, dtype=res.dtype)
486 return result.__finalize__(self, method="concat")
487
C:\Anaconda3\lib\site-packages\pandas\core\series.py in __init__(self, data, index, dtype, name, copy, fastpath)
320 if len(index) != len(data):
321 raise ValueError(
--> 322 f"Length of passed values is {len(data)}, "
323 f"index implies {len(index)}."
324 )
ValueError: Length of passed values is 1, index implies 0.
Traceback for the DataFrame example
C:\Anaconda3\lib\site-packages\pandas\core\reshape\concat.py in concat(objs, axis, join, ignore_index, keys, levels, names, verify_integrity, sort, copy)
296 )
297
--> 298 return op.get_result()
299
300
C:\Anaconda3\lib\site-packages\pandas\core\reshape\concat.py in get_result(self)
519
520 new_data = concatenate_block_managers(
--> 521 mgrs_indexers, self.new_axes, concat_axis=self.bm_axis, copy=self.copy
522 )
523 if not self.copy:
C:\Anaconda3\lib\site-packages\pandas\core\internals\concat.py in concatenate_block_managers(mgrs_indexers, axes, concat_axis, copy)
87 blocks.append(b)
88
---> 89 return BlockManager(blocks, axes)
90
91
C:\Anaconda3\lib\site-packages\pandas\core\internals\managers.py in __init__(self, blocks, axes, do_integrity_check)
141
142 if do_integrity_check:
--> 143 self._verify_integrity()
144
145 # Populate known_consolidate, blknos, and blklocs lazily
C:\Anaconda3\lib\site-packages\pandas\core\internals\managers.py in _verify_integrity(self)
321 for block in self.blocks:
322 if block.shape[1:] != mgr_shape[1:]:
--> 323 raise construction_error(tot_items, block.shape[1:], self.axes)
324 if len(self.items) != tot_items:
325 raise AssertionError(
ValueError: Shape of passed values is (1, 1), indices imply (0, 1)
pd.show_versions()
INSTALLED VERSIONS
------------------
commit : 9d598a5e1eee26df95b3910e3f2934890d062caa
python : 3.8.5.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.17763
machine : AMD64
processor : Intel64 Family 6 Model 63 Stepping 2, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : English_Canada.1252
pandas : 1.2.1
numpy : 1.19.2
pytz : 2020.5
dateutil : 2.8.1
pip : 20.3.3
setuptools : 51.3.3.post20210118
Cython : 0.29.21
pytest : 6.2.1
hypothesis : None
sphinx : 3.4.3
blosc : None
feather : None
xlsxwriter : 1.3.7
lxml.etree : 4.6.2
html5lib : 1.1
pymysql : None
psycopg2 : None
jinja2 : 2.11.2
IPython : 7.19.0
pandas_datareader: None
bs4 : 4.9.3
bottleneck : 1.3.2
fsspec : 0.8.3
fastparquet : None
gcsfs : None
matplotlib : 3.3.2
numexpr : 2.7.2
odfpy : None
openpyxl : 3.0.6
pandas_gbq : None
pyarrow : None
pyxlsb : None
s3fs : None
scipy : 1.5.2
sqlalchemy : 1.3.21
tables : 3.6.1
tabulate : None
xarray : None
xlrd : 2.0.1
xlwt : 1.3.0
numba : 0.51.2