add option_context context manager

RELEASE.rst

@@ -99,7 +99,7 @@ pandas 0.10.0
     instead. This is a legacy hack and can lead to subtle bugs.
   - inf/-inf are no longer considered as NA by isnull/notnull. To be clear, this
     is legacy cruft from early pandas. This behavior can be globally re-enabled
-    using pandas.core.common.use_inf_as_na (#2050, #1919)
+    using the new option ``mode.use_inf_as_null`` (#2050, #1919)
   - ``pandas.merge`` will now default to ``sort=False``. For many use cases
     sorting the join keys is not necessary, and doing it by default is wasteful
   - ``names`` handling in file parsing: if explicit column `names` passed,

doc/source/missing_data.rst

@@ -61,7 +61,7 @@ arise and we wish to also consider that "missing" or "null".
 
 Until recently, for legacy reasons ``inf`` and ``-inf`` were also
 considered to be "null" in computations. This is no longer the case by
-default; use the :func: `~pandas.core.common.use_inf_as_null` function to recover it.
+default; use the ``mode.use_inf_as_null`` option to recover it.
 
 .. _missing.isnull:
 

pandas/core/common.py

@@ -94,8 +94,8 @@ def isnull_old(obj):
     else:
         return obj is None
 
-def use_inf_as_null(flag):
-    '''
+def _use_inf_as_null(key):
+    '''Option change callback for null/inf behaviour
     Choose which replacement for numpy.isnan / -numpy.isfinite is used.
 
     Parameters
@@ -113,6 +113,7 @@ def use_inf_as_null(flag):
     * http://stackoverflow.com/questions/4859217/
       programmatically-creating-variables-in-python/4859312#4859312
     '''
+    flag = get_option(key)
     if flag == True:
         globals()['isnull'] = isnull_old
     else:
@@ -1179,7 +1180,7 @@ def in_interactive_session():
     returns True if running under python/ipython interactive shell
     """
     import __main__ as main
-    return not hasattr(main, '__file__') or get_option('test.interactive')
+    return not hasattr(main, '__file__') or get_option('mode.sim_interactive')
 
 def in_qtconsole():
     """

pandas/core/config.py

@@ -25,7 +25,9 @@
 - all options in a certain sub - namespace can be reset at once.
 - the user can set / get / reset or ask for the description of an option.
 - a developer can register and mark an option as deprecated.
-
+- you can register a callback to be invoked when the the option value
+  is set or reset. Changing the stored value is considered misuse, but
+  is not verboten.
 
 Implementation
 ==============
@@ -54,7 +56,7 @@
 import warnings
 
 DeprecatedOption = namedtuple('DeprecatedOption', 'key msg rkey removal_ver')
-RegisteredOption = namedtuple('RegisteredOption', 'key defval doc validator')
+RegisteredOption = namedtuple('RegisteredOption', 'key defval doc validator cb')
 
 _deprecated_options = {}  # holds deprecated option metdata
 _registered_options = {}  # holds registered option metdata
@@ -65,37 +67,33 @@
 ##########################################
 # User API
 
-def _get_option(pat):
+def _get_single_key(pat, silent):
     keys = _select_options(pat)
     if len(keys) == 0:
-        _warn_if_deprecated(pat)
+        if not silent:
+            _warn_if_deprecated(pat)
         raise KeyError('No such keys(s)')
     if len(keys) > 1:
         raise KeyError('Pattern matched multiple keys')
     key = keys[0]
 
-    _warn_if_deprecated(key)
+    if not silent:
+        _warn_if_deprecated(key)
 
     key = _translate_key(key)
 
+    return key
+
+def _get_option(pat, silent=False):
+    key = _get_single_key(pat,silent)
+
     # walk the nested dict
     root, k = _get_root(key)
-
     return root[k]
 
 
-def _set_option(pat, value):
-
-    keys = _select_options(pat)
-    if len(keys) == 0:
-        _warn_if_deprecated(pat)
-        raise KeyError('No such keys(s)')
-    if len(keys) > 1:
-        raise KeyError('Pattern matched multiple keys')
-    key = keys[0]
-
-    _warn_if_deprecated(key)
-    key = _translate_key(key)
+def _set_option(pat, value, silent=False):
+    key = _get_single_key(pat,silent)
 
     o = _get_registered_option(key)
     if o and o.validator:
@@ -105,6 +103,9 @@ def _set_option(pat, value):
     root, k = _get_root(key)
     root[k] = value
 
+    if o.cb:
+        o.cb(key)
+
 
 def _describe_option(pat='', _print_desc=True):
 
@@ -270,7 +271,29 @@ def __doc__(self):
 ######################################################
 # Functions for use by pandas developers, in addition to User - api
 
-def register_option(key, defval, doc='', validator=None):
+class option_context(object):
+    def __init__(self,*args):
+        assert len(args) % 2 == 0 and len(args)>=2, \
+           "Need to invoke as option_context(pat,val,[(pat,val),..))."
+        ops = zip(args[::2],args[1::2])
+        undo=[]
+        for pat,val in ops:
+            undo.append((pat,_get_option(pat,silent=True)))
+
+        self.undo = undo
+
+        for pat,val in ops:
+            _set_option(pat,val,silent=True)
+
+    def __enter__(self):
+        pass
+
+    def __exit__(self, *args):
+        if self.undo:
+            for pat, val in self.undo:
+                _set_option(pat, val)
+
+def register_option(key, defval, doc='', validator=None, cb=None):
     """Register an option in the package-wide pandas config object
 
     Parameters
@@ -280,6 +303,9 @@ def register_option(key, defval, doc='', validator=None):
     doc       - a string description of the option
     validator - a function of a single argument, should raise `ValueError` if
                 called with a value which is not a legal value for the option.
+    cb        - a function of a single argument "key", which is called
+                immediately after an option value is set/reset. key is
+                the full name of the option.
 
     Returns
     -------
@@ -321,7 +347,7 @@ def register_option(key, defval, doc='', validator=None):
 
     # save the option metadata
     _registered_options[key] = RegisteredOption(key=key, defval=defval,
-            doc=doc, validator=validator)
+            doc=doc, validator=validator,cb=cb)
 
 
 def deprecate_option(key, msg=None, rkey=None, removal_ver=None):

pandas/core/config_init.py

@@ -139,10 +139,27 @@
     cf.register_option('expand_frame_repr', True, pc_expand_repr_doc)
     cf.register_option('line_width', 80, pc_line_width_doc)
 
-tc_interactive_doc="""
+tc_sim_interactive_doc="""
 : boolean
     Default False
     Whether to simulate interactive mode for purposes of testing
 """
-with cf.config_prefix('test'):
-    cf.register_option('interactive', False, tc_interactive_doc)
+with cf.config_prefix('mode'):
+    cf.register_option('sim_interactive', False, tc_sim_interactive_doc)
+
+use_inf_as_null_doc="""
+: boolean
+    True means treat None, NaN, INF, -INF as null (old way),
+    False means None and NaN are null, but INF, -INF are not null
+    (new way).
+"""
+
+# we don't want to start importing evrything at the global context level
+# or we'll hit circular deps.
+def use_inf_as_null_cb(key):
+    from pandas.core.common import _use_inf_as_null
+    _use_inf_as_null(key)
+
+with cf.config_prefix('mode'):
+    cf.register_option('use_inf_as_null', False, use_inf_as_null_doc,
+                       cb=use_inf_as_null_cb)

pandas/tests/test_common.py

@@ -5,9 +5,10 @@
 import unittest
 
 from pandas import Series, DataFrame, date_range, DatetimeIndex
-from pandas.core.common import notnull, isnull, use_inf_as_null
+from pandas.core.common import notnull, isnull
 import pandas.core.common as com
 import pandas.util.testing as tm
+import pandas.core.config as cf
 
 import numpy as np
 
@@ -29,20 +30,19 @@ def test_notnull():
     assert not notnull(None)
     assert not notnull(np.NaN)
 
-    use_inf_as_null(False)
-    assert notnull(np.inf)
-    assert notnull(-np.inf)
+    with cf.option_context("mode.use_inf_as_null",False):
+        assert notnull(np.inf)
+        assert notnull(-np.inf)
 
-    use_inf_as_null(True)
-    assert not notnull(np.inf)
-    assert not notnull(-np.inf)
+    with cf.option_context("mode.use_inf_as_null",True):
+        assert not notnull(np.inf)
+        assert not notnull(-np.inf)
 
-    use_inf_as_null(False)
-
-    float_series = Series(np.random.randn(5))
-    obj_series = Series(np.random.randn(5), dtype=object)
-    assert(isinstance(notnull(float_series), Series))
-    assert(isinstance(notnull(obj_series), Series))
+    with cf.option_context("mode.use_inf_as_null",False):
+        float_series = Series(np.random.randn(5))
+        obj_series = Series(np.random.randn(5), dtype=object)
+        assert(isinstance(notnull(float_series), Series))
+        assert(isinstance(notnull(obj_series), Series))
 
 def test_isnull():
     assert not isnull(1.)

pandas/tests/test_config.py

@@ -282,6 +282,46 @@ def test_config_prefix(self):
             self.assertEqual(self.cf.get_option('a'), 1)
             self.assertEqual(self.cf.get_option('b'), 2)
 
+    def test_callback(self):
+        k=[None]
+        v=[None]
+        def callback(key):
+            k.append(key)
+            v.append(self.cf.get_option(key))
+
+        self.cf.register_option('d.a', 'foo',cb=callback)
+        self.cf.register_option('d.b', 'foo',cb=callback)
+
+        del k[-1],v[-1]
+        self.cf.set_option("d.a","fooz")
+        self.assertEqual(k[-1],"d.a")
+        self.assertEqual(v[-1],"fooz")
+
+        del k[-1],v[-1]
+        self.cf.set_option("d.b","boo")
+        self.assertEqual(k[-1],"d.b")
+        self.assertEqual(v[-1],"boo")
+
+        del k[-1],v[-1]
+        self.cf.reset_option("d.b")
+        self.assertEqual(k[-1],"d.b")
+
+
+    def test_set_ContextManager(self):
+        def eq(val):
+            self.assertEqual(self.cf.get_option("a"),val)
+
+        self.cf.register_option('a',0)
+        eq(0)
+        with self.cf.option_context("a",15):
+            eq(15)
+            with self.cf.option_context("a",25):
+                eq(25)
+            eq(15)
+        eq(0)
+
+        self.cf.set_option("a",17)
+        eq(17)
 
 # fmt.reset_printoptions and fmt.set_printoptions were altered
 # to use core.config, test_format exercises those paths.