Pandas Unexpected behaviour while dropping

Code Sample, a copy-pastable example if possible

>>> ser = pd.Series([f for f in 'abcdefgh'])
>>> ser.drop(ser == 'c')

2    c
3    d
4    e
5    f
6    g
7    h
dtype: object

Problem description

I see what is going here, ser == 'c' results in a list of True/False (meaning 0 and 1), so it drops the 0 and 1 indices. However, this is a completely unexpected result. This should at least raise an exception. I would be happy with an error, but boolean mask support would result in a much more cleaner and simpler syntax than:

ser.drop(ser[ser == 'c'].index)

Expected Output

Raising an exception or dropping by boolean mask:

0    a
1    b
3    d
4    e
5    f
6    g
7    h
dtype: object

Output of `pd.show_versions()`

INSTALLED VERSIONS ------------------ commit: None pandas: 0.19.2 nose: None pip: 9.0.1 setuptools: 36.6.0 Cython: None numpy: 1.11.0 scipy: 0.18.1 statsmodels: None xarray: None IPython: 6.2.1 sphinx: 1.6.4 patsy: None dateutil: 2.6.1 pytz: 2017.2 blosc: None bottleneck: None tables: None numexpr: None matplotlib: 2.1.0 openpyxl: None xlrd: None xlwt: None xlsxwriter: None lxml: None bs4: None html5lib: None httplib2: None apiclient: None sqlalchemy: None pymysql: None psycopg2: None jinja2: 2.9.6 boto: None pandas_datareader: None

Comment From: jorisvandenbossche

This is fixed in pandas 0.21.0, and it now raises an error:

In [195]: ser = pd.Series([f for f in 'abcdefgh'])

In [196]: ser.drop(ser == 'c')
...
ValueError: labels [False False  True False False False False False] not contained in axis

(see https://github.com/pandas-dev/pandas/issues/16877, PR https://github.com/pandas-dev/pandas/pull/17343)

Comment From: carlosdanielcsantos

@jorisvandenbossche how about being able to drop with boolean mask? Is there any discussion going on about it?