fix to_datetime default error suppression

[cowpig]

No description provided.

[jreback]

• its not nice to change kwarg names without a deprecation cycle.
• why do you think this is a good idea?
• I think you could only realistically do this with an option that you could optionally set,
  e.g. change the kwarg to None then if its None use the default value of the option (I am talking
  about pd.set_option(....) here)
• this would need a fair amount of tests for this change

[cowpig]

I can see how switching to a boolean can break things, but ignoring errors by default is quite bad. How about I start by just changing the default?

[jreback]

@cowpig well, the problem is pd.to_datetime will not barf on valid but non-parseable datelikes now.

eg.

In [27]: pd.to_datetime('19MAY11',errors='raise')
TypeError: 'NoneType' object is not iterable

In [28]: pd.to_datetime('19MAY11',errors='raise',coerce=True)
Out[28]: NaT

In [29]: pd.to_datetime('19MAY11',errors='raise',format='%d%b%y')
Out[29]: Timestamp('2011-05-19 00:00:00')

So that error message is pretty bad. If you chane the default, then see what error message happens, and could think about doing that. I am not averse, its just that this affects lots of things possibly in subtle way.

[vfilimonov]

I think it belongs here:

date format "%Y%m%d" does not raise errors even when errors='raise' and silently returns datetime.datetime for out of bounds timestamp:

>>> pd.to_datetime('1300-01-01', format='%Y-%m-%d', errors='raise')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users//.virtual_envs/system/lib/python2.7/site-packages/pandas/tseries/tools.py", line 318, in to_datetime
    return _convert_listlike(np.array([ arg ]), box, format)[0]
  File "/Users//.virtual_envs/system/lib/python2.7/site-packages/pandas/tseries/tools.py", line 306, in _convert_listlike
    raise e
pandas.tslib.OutOfBoundsDatetime: Out of bounds nanosecond timestamp: 1300-01-01 00:00:00
>>> pd.to_datetime('13000101', format='%Y%m%d', errors='raise')
datetime.datetime(1300, 1, 1, 0, 0)

[jreback]

closing pls reopen if/when updated