Change hasattr to callable (has2k1#421)

Author: Alyetama

.gitignore

@@ -55,7 +55,7 @@ examples/.ipynb_checkpoints
 *.mo
 *.pot
 
-# Django stuff:
+# Django stuff
 *.log
 
 # Sphinx documentation
@@ -65,3 +65,7 @@ doc/generated/
 # PyBuilder
 target/
 
+# OS generated files
+.DS_Store
+.DS_Store?
+

plotnine/layer.py

@@ -249,7 +249,7 @@ def generate_data(self, plot_data):
                     "{} layer expects a dataframe, but it got "
                     "{} instead.".format(_geom_name, _data_name)
                 )
-        elif hasattr(self.data, '__call__'):
+        elif callable(self.data):
             self.data = self.data(plot_data)
             if not isinstance(self.data, pd.DataFrame):
                 raise PlotnineError(

plotnine/stats/smoothers.py

@@ -37,7 +37,7 @@ def predictdf(data, xseq, **params):
             msg = "Method should be one of {}"
             raise PlotnineError(msg.format(list(methods.keys())))
 
-    if not hasattr(method, '__call__'):
+    if not callable(method):
         msg = ("'method' should either be a string or a function"
                "with the signature `func(data, xseq, **params)`")
         raise PlotnineError()

plotnine/stats/stat_function.py

@@ -62,7 +62,7 @@ def compute_group(cls, data, scales, **params):
             raise PlotnineError(
                 "Missing 'x' aesthetic and 'xlim' is {}".format(xlim))
 
-        if not hasattr(fun, '__call__'):
+        if not callable(fun):
             raise PlotnineError(
                 "stat_function requires parameter 'fun' to be " +
                 "a function or any other callable object")