Wolfram Computation Meets Knowledge

CreatePackageEventHandler

Contributed by: Richard Hennigan (Wolfram Research)

Create an event handler that evaluates an expression when a package is loaded

ResourceFunction["CreatePackageEventHandler"][code,"context`"]

creates an event handler that evaluates code when "context`" starts loading.

ResourceFunction["CreatePackageEventHandler"][code,"context`",After]

creates an event handler that evaluates code when "context`" finishes loading.

Details and Options

ResourceFunction["CreatePackageEventHandler"][code,"context`",Before] is equivalent to ResourceFunction["CreatePackageEventHandler"][code,"context`"].

Examples

Basic Examples

Print a message when a package is first loaded:

In[1]:=
ResourceFunction["CreatePackageEventHandler"][
 Print["Loading ComputerArithmetic`\[Ellipsis]"], \
"ComputerArithmetic`"]
Out[1]=
In[2]:=
Needs["ComputerArithmetic`"]

Print a message when a package finishes loading:

In[3]:=
ResourceFunction["CreatePackageEventHandler"][
 Print[Length[Names["Notation`*"]], " symbols loaded in Notation`."], "Notation`", After]
Out[3]=
In[4]:=
Needs["Notation`"]

Check to see what file is used to load a context:

In[5]:=
ResourceFunction["CreatePackageEventHandler"][
 Print["Loading QuantityUnits` from ", $InputFileName], \
"QuantityUnits`"]
Out[5]=
In[6]:=
GeoNearest["City", Here]
Out[6]=

Get timing for loading a package:

In[7]:=
CloudGet["https://www.wolframcloud.com/objects/4330bcb7-a908-4c92-9155-751b8d383706"] (* Evaluate this cell to copy the example input from a cloud object *)
Out[9]=

Possible Issues

An auto-loading context that is already loaded will no longer trigger the loading event:

In[10]:=
ResourceFunction["CreatePackageEventHandler"][
 Print["Loading NeuralNetworks` from ", $InputFileName], \
"NeuralNetworks`"]
Out[10]=
In[11]:=
NetModel["LeNet Trained on MNIST Data"][{\!\(\*
GraphicsBox[
TagBox[RasterBox[CompressedData["
1:eJxTTMoPSmNiYGAo5gASQYnljkVFiZXBAkBOaF5xZnpeaopnXklqemqRRRJI
mQwU/6cK2MHQhEtqiTTTJVxyQUy633BIneZSeolLWwSTBS6pP1ZM+bjkzjEJ
4ZL6X81kjkvqKydTHS65L0y45c4wMS3FJdfOxHRtcW3tkY/Y5cBA+T5WOaPk
5GgmJkNMOQWwW/6FMMliyqWB5X46MlliNTPo//+JTExbMOU+Ad0h683ElP8P
U+73fCGQM4XuYPHD//97LZmYLPdhlRrUAABgHMjK
"], {{0, 28}, {28, 0}}, {0, 255},
ColorFunction->GrayLevel],
BoxForm`ImageTag[
      "Byte", ColorSpace -> Automatic, Interleaving -> None],
Selectable->False],
DefaultBaseStyle->"ImageGraphics",
ImageSizeRaw->{28, 28},
PlotRange->{{0, 28}, {0, 28}}]\), \!\(\*
GraphicsBox[
TagBox[RasterBox[CompressedData["
1:eJxTTMoPSmNiYGAo5gASQYnljkVFiZXBAkBOaF5xZnpeaopnXklqemqRRRJI
mQwU/x9IsJWBKew2dql3okzMzH6/sMr5M7tPNGWeglXOQPf//yPiZdjlgMI7
mbHKVTOVQQkM8FCaef+v3dIih7HIfQphnnKCmdntBzYzdzKLizEzM+/DJvdD
hxnoP+xueafNxCvJwWSG3S0SV/+7M/tikbvAzHzyP1AOi5lvNJj9fwPlVJdj
ytUzMx8HUu7xWIw0ZdJ49f/PJUWTL5hyTMwT//+/xMxcgkUfE/Ou/92KzKGf
sMqpGLBzTb6MRer/Sh1gmGDzG/0AACEauS8=
"], {{0, 28}, {28, 0}}, {0, 255},
       
ColorFunction->GrayLevel],
BoxForm`ImageTag[
      "Byte", ColorSpace -> Automatic, Interleaving -> None],
Selectable->False],
DefaultBaseStyle->"ImageGraphics",
ImageSizeRaw->{28, 28},
PlotRange->{{0, 28}, {0, 28}}]\), \!\(\*
GraphicsBox[
TagBox[RasterBox[CompressedData["
1:eJxTTMoPSmNiYGAo5gASQYnljkVFiZXBAkBOaF5xZnpeaopnXklqemqRRRJI
mQwU/x9IsN/BdW1Vstx8LFK7eZgYmYBAcepvNJkvG/mZIHJMTLfR5OaBBAtX
r44CKqn4hSK1TRgoZQNipQEZp5ClPpoCRSr+gJiXgarykeWWAqUqoSalocrd
52ViCnwJMx5VLpeJyQVufyOK3Fo2JqYWOM+WiWkFkjZGRjs4p4mRkXE5nPcp
GegQGOeXM9BZ1vth3EAgT3I+lHMOyLE7Adf3y4uJqeY1hP3MFShXhbDuTwgT
0ywIa5s9Wnh+AnIFErYBgSVIRrz4G0LumxoTFIDiQaztPzLIQ5JzPogi9f+Z
NkzOof77fzTwY1EcSKps5y90GToCAMITbxU=
"], {{0, 28}, {28, 0}}, {0, 255},
       
ColorFunction->GrayLevel],
BoxForm`ImageTag[
      "Byte", ColorSpace -> Automatic, Interleaving -> None],
Selectable->False],
DefaultBaseStyle->"ImageGraphics",
ImageSizeRaw->{28, 28},
PlotRange->{{0, 28}, {0, 28}}]\)}]
Out[11]=

Run in a new session instead:

In[12]:=
ResourceFunction["LocalEvaluate"][
 NetModel["LeNet Trained on MNIST Data"][{\!\(\*
GraphicsBox[
TagBox[RasterBox[CompressedData["
1:eJxTTMoPSmNiYGAo5gASQYnljkVFiZXBAkBOaF5xZnpeaopnXklqemqRRRJI
mQwU/6cK2MHQhEtqiTTTJVxyQUy633BIneZSeolLWwSTBS6pP1ZM+bjkzjEJ
4ZL6X81kjkvqKydTHS65L0y45c4wMS3FJdfOxHRtcW3tkY/Y5cBA+T5WOaPk
5GgmJkNMOQWwW/6FMMliyqWB5X46MlliNTPo//+JTExbMOU+Ad0h683ElP8P
U+73fCGQM4XuYPHD//97LZmYLPdhlRrUAABgHMjK
"], {{0, 28}, {28, 0}}, {0, 255},
ColorFunction->GrayLevel],
BoxForm`ImageTag[
       "Byte", ColorSpace -> Automatic, Interleaving -> None],
Selectable->False],
DefaultBaseStyle->"ImageGraphics",
ImageSizeRaw->{28, 28},
PlotRange->{{0, 28}, {0, 28}}]\), \!\(\*
GraphicsBox[
TagBox[RasterBox[CompressedData["
1:eJxTTMoPSmNiYGAo5gASQYnljkVFiZXBAkBOaF5xZnpeaopnXklqemqRRRJI
mQwU/x9IsJWBKew2dql3okzMzH6/sMr5M7tPNGWeglXOQPf//yPiZdjlgMI7
mbHKVTOVQQkM8FCaef+v3dIih7HIfQphnnKCmdntBzYzdzKLizEzM+/DJvdD
hxnoP+xueafNxCvJwWSG3S0SV/+7M/tikbvAzHzyP1AOi5lvNJj9fwPlVJdj
ytUzMx8HUu7xWIw0ZdJ49f/PJUWTL5hyTMwT//+/xMxcgkUfE/Ou/92KzKGf
sMqpGLBzTb6MRer/Sh1gmGDzG/0AACEauS8=
"], {{0, 28}, {28, 0}}, {0, 255},
        
ColorFunction->GrayLevel],
BoxForm`ImageTag[
       "Byte", ColorSpace -> Automatic, Interleaving -> None],
Selectable->False],
DefaultBaseStyle->"ImageGraphics",
ImageSizeRaw->{28, 28},
PlotRange->{{0, 28}, {0, 28}}]\), \!\(\*
GraphicsBox[
TagBox[RasterBox[CompressedData["
1:eJxTTMoPSmNiYGAo5gASQYnljkVFiZXBAkBOaF5xZnpeaopnXklqemqRRRJI
mQwU/x9IsN/BdW1Vstx8LFK7eZgYmYBAcepvNJkvG/mZIHJMTLfR5OaBBAtX
r44CKqn4hSK1TRgoZQNipQEZp5ClPpoCRSr+gJiXgarykeWWAqUqoSalocrd
52ViCnwJMx5VLpeJyQVufyOK3Fo2JqYWOM+WiWkFkjZGRjs4p4mRkXE5nPcp
GegQGOeXM9BZ1vth3EAgT3I+lHMOyLE7Adf3y4uJqeY1hP3MFShXhbDuTwgT
0ywIa5s9Wnh+AnIFErYBgSVIRrz4G0LumxoTFIDiQaztPzLIQ5JzPogi9f+Z
NkzOof77fzTwY1EcSKps5y90GToCAMITbxU=
"], {{0, 28}, {28, 0}}, {0, 255},
        
ColorFunction->GrayLevel],
BoxForm`ImageTag[
       "Byte", ColorSpace -> Automatic, Interleaving -> None],
Selectable->False],
DefaultBaseStyle->"ImageGraphics",
ImageSizeRaw->{28, 28},
PlotRange->{{0, 28}, {0, 28}}]\)}],
 HandlerFunctions -> <|
   "PrintOutputGenerated" -> (Print[ReleaseHold[#PrintOutput]] &)|>,
 Initialization :> (ResourceFunction["CreatePackageEventHandler"][
    Print["Loading NeuralNetworks` from ", $InputFileName], "NeuralNetworks`"])
 ]
Out[12]=

Resource History