New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

first_valid_index fails when dataframe has non-unique row index #21441

Closed
adamklein opened this Issue Jun 12, 2018 · 1 comment

Comments

Projects
None yet
3 participants
@adamklein
Contributor

adamklein commented Jun 12, 2018

Code Sample, a copy-pastable example if possible

In [2]: import pandas as pd

In [3]: pd.__version__
Out[3]: '0.23.0rc2'

In [4]: x = pd.DataFrame({'b': [1,2,3]}, index=[1,1,2])

In [5]: x
Out[5]: 
   b
1  1
1  2
2  3

In [6]: x.first_valid_index()
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-6-baa2c482d9a6> in <module>()
----> 1 x.first_valid_index()

lib/python3.5/site-packages/pandas/core/generic.py in first_valid_index(self)
   8881                                              'klass': 'NDFrame'})
   8882     def first_valid_index(self):
-> 8883         return self._find_valid_index('first')
   8884 
   8885     @Appender(_shared_docs['valid_index'] % {'position': 'last',

lib/python3.5/site-packages/pandas/core/generic.py in _find_valid_index(self, how)
   8867             # First valid value case
   8868             i = is_valid.idxmax()
-> 8869             if not is_valid[i]:
   8870                 return None
   8871             return i

lib/python3.5/site-packages/pandas/core/generic.py in __nonzero__(self)
   1572         raise ValueError("The truth value of a {0} is ambiguous. "
   1573                          "Use a.empty, a.bool(), a.item(), a.any() or a.all()."
-> 1574                          .format(self.__class__.__name__))
   1575 
   1576     __bool__ = __nonzero__

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

Problem description

first_valid_index did not raise on a row index with duplicate values on pandas <= 0.22.0

Expected Output

0

Output of pd.show_versions()

INSTALLED VERSIONS

commit: None
python: 3.5.4.final.0
python-bits: 64
OS: Linux
OS-release: 4.1.35-pv-ts2
machine: x86_64
processor:
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.23.0
pytest: 3.2.1
pip: 9.0.1
setuptools: 36.4.0
Cython: None
numpy: 1.12.1
scipy: 0.19.1
pyarrow: 0.8.0
xarray: None
IPython: 6.1.0
sphinx: 1.7.5
patsy: 0.4.1
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: None
tables: 3.4.2
numexpr: 2.6.2
feather: None
matplotlib: 2.0.2
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: 4.6.0
html5lib: 0.9999999
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None

cc @jreback

@gfyoung gfyoung added this to the 0.23.2 milestone Jun 13, 2018

@KalyanGokhale

This comment has been minimized.

Contributor

KalyanGokhale commented Jun 15, 2018

Expected Output

0

@adamklein in your example, did you mean the Expect Output was 1 ?

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment