BUG: Series.equals fails when comparing numpy arrays to scalars

[avinashpancham]

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• (optional) I have confirmed this bug exists on the master branch of pandas.

---

Note: Please read this guide detailing how to provide the necessary information for us to reproduce your bug.

Code Sample, a copy-pastable example

import pandas as pd
import numpy as np

arr = np.array([1, 2])
s1 = pd.Series([arr, arr])
s2 = s1.copy()

s1[1] = 9
s1.equals(s2) # This throws a ValueError

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Problem description

Series.equals operation fails when comparing two Series that at the same position respectively have a single value and a list. Pandas then throws a ValueError since it cannot compare a single value to a list.

Related issues #20676 and #35237

Expected Output

False, since the two series are not equal

Output of pd.show_versions()

INSTALLED VERSIONS

commit : 9827ce0
python : 3.8.3.final.0
python-bits : 64
OS : Darwin
OS-release : 19.5.0
Version : Darwin Kernel Version 19.5.0: Tue May 26 20:41:44 PDT 2020; root:xnu-6153.121.2~2/RELEASE_X86_64
machine : x86_64
processor : i386
byteorder : little
LC_ALL : None
LANG : None
LOCALE : None.UTF-8

pandas : 1.1.0.dev0+2088.g9827ce00f
numpy : 1.18.5
pytz : 2020.1
dateutil : 2.8.1
pip : 20.1.1
setuptools : 49.2.0.post20200712
Cython : 0.29.21
pytest : 5.4.3
hypothesis : 5.19.1
sphinx : 3.1.1
blosc : None
feather : None
xlsxwriter : 1.2.9
lxml.etree : 4.5.2
html5lib : 1.1
pymysql : None
psycopg2 : None
jinja2 : 2.11.2
IPython : 7.16.1
pandas_datareader: None
bs4 : 4.9.1
bottleneck : 1.3.2
fsspec : 0.7.4
fastparquet : 0.4.0
gcsfs : 0.6.2
matplotlib : 3.2.2
numexpr : 2.7.1
odfpy : None
openpyxl : 3.0.4
pandas_gbq : None
pyarrow : 0.17.1
pytables : None
pyxlsb : None
s3fs : 0.4.2
scipy : 1.5.0
sqlalchemy : 1.3.18
tables : 3.6.1
tabulate : 0.8.7
xarray : 0.16.0
xlrd : 1.2.0
xlwt : 1.3.0
numba : 0.50.1

[avinashpancham]

If we decide to go ahead and fix this bug then I would like to contribute. I'm still a beginner, so if someone can point me in the right direction it would be very helpful!

[Dr-Irv]

@avinashpancham can you put a better title on this issue?

[avinashpancham]

Sorry, saw that I forgot to edit the title. Updated it.

[TomAugspurger]

This looks lie a bug, but I'm not sure where best to fix it. Investigation would be welcome.

[avinashpancham]

I can have a look at it this weekend

[avinashpancham]

Extending array_equivalent_object in _libs/lib.pyx seemed like the best way to solve this issue. What do you think?