ENH: Support inplace clip (pandas-dev#15388)

Author: guygoldberg

pandas/core/generic.py

@@ -4119,8 +4119,7 @@ def isnull(self):
     def notnull(self):
         return notnull(self).__finalize__(self)
 
-    def _clip_with_scalar(self, lower, upper):
-
+    def _clip_with_scalar(self, lower, upper, inplace=False):
         if ((lower is not None and np.any(isnull(lower))) or
                 (upper is not None and np.any(isnull(upper)))):
             raise ValueError("Cannot use an NA value as a clip threshold")
@@ -4136,10 +4135,15 @@ def _clip_with_scalar(self, lower, upper):
         if np.any(mask):
             result[mask] = np.nan
 
-        return self._constructor(
-            result, **self._construct_axes_dict()).__finalize__(self)
+        axes_dict = self._construct_axes_dict()
+        result = self._constructor(result, **axes_dict).__finalize__(self)
+
+        if inplace:
+            self._update_inplace(result)
+        else:
+            return result
 
-    def clip(self, lower=None, upper=None, axis=None, *args, **kwargs):
+    def clip(self, lower=None, upper=None, axis=None, inplace=False, *args, **kwargs):
         """
         Trim values at input threshold(s).
 
@@ -4201,17 +4205,17 @@ def clip(self, lower=None, upper=None, axis=None, *args, **kwargs):
         # fast-path for scalars
         if ((lower is None or (is_scalar(lower) and is_number(lower))) and
                 (upper is None or (is_scalar(upper) and is_number(upper)))):
-            return self._clip_with_scalar(lower, upper)
+            return self._clip_with_scalar(lower, upper, inplace=inplace)
 
         result = self
         if lower is not None:
-            result = result.clip_lower(lower, axis)
+            result = result.clip_lower(lower, axis, inplace=inplace)
         if upper is not None:
-            result = result.clip_upper(upper, axis)
+            result = result.clip_upper(upper, axis, inplace=inplace)
 
         return result
 
-    def clip_upper(self, threshold, axis=None):
+    def clip_upper(self, threshold, axis=None, inplace=False):
         """
         Return copy of input with values above given value(s) truncated.
 
@@ -4233,12 +4237,12 @@ def clip_upper(self, threshold, axis=None):
             raise ValueError("Cannot use an NA value as a clip threshold")
 
         if is_scalar(threshold) and is_number(threshold):
-            return self._clip_with_scalar(None, threshold)
+            return self._clip_with_scalar(None, threshold, inplace=inplace)
 
         subset = self.le(threshold, axis=axis) | isnull(self)
-        return self.where(subset, threshold, axis=axis)
+        return self.where(subset, threshold, axis=axis, inplace=inplace)
 
-    def clip_lower(self, threshold, axis=None):
+    def clip_lower(self, threshold, axis=None, inplace=False):
         """
         Return copy of the input with values below given value(s) truncated.
 
@@ -4260,10 +4264,10 @@ def clip_lower(self, threshold, axis=None):
             raise ValueError("Cannot use an NA value as a clip threshold")
 
         if is_scalar(threshold) and is_number(threshold):
-            return self._clip_with_scalar(threshold, None)
+            return self._clip_with_scalar(threshold, None, inplace=inplace)
 
         subset = self.ge(threshold, axis=axis) | isnull(self)
-        return self.where(subset, threshold, axis=axis)
+        return self.where(subset, threshold, axis=axis, inplace=inplace)
 
     def groupby(self, by=None, axis=0, level=None, as_index=True, sort=True,
                 group_keys=True, squeeze=False, **kwargs):