Libraries

To create a C# library, open a terminal in one of your workspaces and then create a project in the Library directory.

$ lean project-create "Library/MyLibrary" --language csharp
Successfully created C# project 'Library/MyLibrary'

Follow these steps to use a C# library in a C# project:

1. Open a terminal in one of your workspaces.
2. Run lean library add "<projectName>" "Library/<libraryName>".

   $ lean library add "My Project" "Library/MyLibrary"
   Adding Lean CLI library D:\qc\lean-cli\Library\MyLibrary to project D:\qc\lean-cli\My Project
   Restoring packages in 'My Project' to provide local autocomplete: D:\qc\lean-cli\My Project, D:\qc\lean-cli\My Project\My Project.csproj, D:\qc\lean-cli

3. In your project files, add the library namespace to the top of the page.

   By default, the namespace is QuantConnect.

   using QuantConnect;
   

4. In your project files, instantiate the library class and call its methods.

   var x = new MyLibrary();
   var value = x.Add(1, 2);

To create a Python library, open a terminal in one of your workspaces and then create a project in the Library directory.

$ lean project-create "Library/MyLibrary" --language python
Successfully created Python project 'Library/MyLibrary'

The library name can only contain letters (a-z), numbers (0-9), and underscores (_). The name can't contain spaces or start with a number.

Follow these steps to use a Python library in a Python project:

1. Open a terminal in one of your workspaces.
2. Run lean library add "<projectName>" "Library/<libraryName>".

   $ lean library add "My Project" "Library/MyLibrary"
   Adding Lean CLI library D:\qc\lean-cli\Library\MyLibrary to project D:\qc\lean-cli\Library Test

3. In your project files, import the library class at the top of the page.

   from MyLibrary.main import MyLibrary
   

   In general, use from <libraryName>.<fileNameWithoutExtension> import <memberName>.

4. In your project files, instantiate the library class and call its methods.

   x = MyLibrary()
   value = x.Add(1, 2)