CLN/BUG: remove bare excepts

[jburroni]

Using KeyError may prevent the system to show system error, and thus make the error hard to find

df = pd.DataFrame({'a':[1,]}, index=['a'])
def bla(a):
    return bla(df.loc[['a'], ['a']])
bla(1)

Expected Output

Max recursion limit exception. Got key error

Output of pd.show_versions()

INSTALLED VERSIONS ------------------ commit: None python: 2.7.12.final.0 python-bits: 64 OS: Darwin OS-release: 15.6.0 machine: x86_64 processor: i386 byteorder: little LC_ALL: en_US.UTF-8 LANG: en_US.UTF-8

pandas: 0.18.1
nose: 1.3.7
pip: None
setuptools: None
Cython: None
numpy: 1.11.2
scipy: 0.18.1
statsmodels: None
xarray: None
IPython: 5.1.0
sphinx: None
patsy: None
dateutil: 2.5.3
pytz: 2016.7
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: 1.5.3
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: 4.4.1
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.8
boto: None
pandas_datareader: None

[jreback]

what exactly is a KeyError?

This evaluates correctly to an infinite recursion.

[jburroni]

This is the KeyError (there was a little bug in the code snippet).
I'm using python 2.7
/../Library/Python/2.7/lib/python/site-packages/pandas/core/indexing.pyc in _multi_take(self, tup)
838 return o.reindex(**d)
839 except:
--> 840 raise self._exception
841
842 def _convert_for_reindex(self, key, axis=0):

KeyError: 

[jreback]

and?

[jburroni]

That there is no key error. The exception should be "max recursion limit",
but it was hid by the indexer. This makes the situation very hard to debug

On Tuesday, November 1, 2016, Jeff Reback [email protected] wrote:

and?

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[jreback]

I am still not clear what exactly is the issue. you have a recursion issue. This pandas call returns a valid value. What do you think this should do?

[jburroni]

Part of the issue is in here:
https://github.com/pandas-dev/pandas/blob/master/pandas/core/indexing.py#L55
where the default exception is set to KeyError
Then, in
https://github.com/pandas-dev/pandas/blob/master/pandas/core/indexing.py#L850
all exception are caught and converted to KeyError. In the example above, the previous line will rise a RuntimeError with 'maximum recursion depth exceeded' but it will be caught and transformed in KeyError, which is incorrect (and misleading).
There are 6 extra 'except:' in that file. (And those are not recommended)

[jreback]

sure. bare excepts are not recommended
submitting a pr is the best way to fix