Run and debug Jupyter notebook code cells

You can execute the code of notebook cells in many ways using the icons on the notebook toolbar, commands in the code cell context menu, and the Run icon in the gutter.

Run code cells

Use the following smart shortcuts to quickly run the code cells:
- Ctrl+Enter: Runs the current cell.
- Shift+Enter: Runs the current cell and selects the cell below it.
When executing one cell at a time, mind code dependencies. If a cell relies on some code in another cell, that cell should be executed first.
When the execution is done, the cell remains in the edit mode so that you can modify it, if needed, and keep experimenting.
To execute all code cells in your notebook, click on the notebook toolbar.

You can find the information about the duration of a cell execution in the lower left corner of the cell.
Hover over this area to view the date and time when the cell execution was completed.
In case of any errors, expand the Traceback node to view the complete error message.

When you stop the server and change the server or kernel, you have to execute all cells with dependencies again because execution results are valid for the current server session only.

View variables

Jupyter Variables tool window

When you execute your notebook, you can preview variables in the Jupyter Variables tool window

Jupyter server tool window: the Variables tab

You can click the link to the right of the variable to preview its values in the tabular form.

Data Vision

You can also preview variables right in the editor.

Go to Settings | Languages & Frameworks | Jupyter and make sure that the Show inline values checkbox is enabled.

Run the notebook cell. The values of variables are shown next to their usages:
Values of specific types, for example, pandas DataFrames and numpy arrays, can't be rendered inline. To view them in the tabular form, hover over the value and click the down arrow:
Click the variable to view detailed information in a popup.

Preview reference documentation

With DataSpell you can always quickly preview reference documentation for a particular variable, type, or argument.

To view reference information for any element of a particular code cell, place the caret within the target code cell and type ? <type/variable/argument>. (in this example, you will preview documentation for plt.scatter). Note that a code element should be accessible within the code cell.
Execute the cell. The Introspection tab opens in the Jupyter tool window.
Preview reference documentation in the Introspection tab.

Note that the Introspection tab shows documentation for the latest requested code element. Even though you proceed with executing other code cells, restart the server, or delete the line with your request, this information will be shown.

Debug code in Jupyter notebooks

DataSpell provides the Jupyter Notebook Debugger for both local and remote Jupyter server kernels.

Set the breakpoints in the selected cell and click Debug Cell in the notebook toolbar. Alternatively, you can right-click the cell and select Debug Cell from the context menu.
The Jupyter Notebook Debugger tool window opens.
Use the stepping toolbar buttons to choose on which line you want to stop next.
Debugging is performed within a single code cell. However, if your code cell calls a function from any cell that has been already debugged, you can step into it. The related breakpoints will also work. Note that the cell with the function must be debugged, not just executed.
The debugger may skip a cell if you change its source code or execute it not under the debugger. Also, you can see a warning message when trying to modify the cell code during the debugging session.
Similarly, you can step into a function called from a Python file that is located in the same project.
Proceed with the debugging steps to complete the execution of the cell.

Item	Tooltip and Shortcut	Description
Action available on the Debugger toolbar.
	Step Over `F8`	Click this button to execute the program until the next line in the current method or file, skipping the methods referenced at the current execution point (if any). If the current line is the last one in the method, execution steps to the line are executed right after this method.
	Step Into `F7`	Click this button to have the debugger step into the method called at the current execution point.
	Step Out `Shift+F8`	Click this button to have the debugger step out of the current method, to the line executed right after it.
Additional stepping actions available by clicking on the Debugger toolbar.
	Force Step Over `Alt+Shift+F8`	Steps over the current line of code and takes you to the next line even if the highlighted line has method calls in it. If there are breakpoints in the called methods, they are ignored.
	Force Step Into `Alt+Shift+F7`	Click this button to have the debugger step into the method called in the current execution point even if this method is to be skipped.
	Smart Step Into `Shift+F7`	Smart step into is helpful when there are several method calls on a line, and you want to be specific about which method to enter. This feature allows you to select the method call you are interested in.
	Run to Cursor `Alt+F9`	Click this button to resume program execution and pause until the execution point reaches the line at the current caret location in the editor. No breakpoint is required. Actually, there is a temporary breakpoint set for the current line at the caret, which is removed once program execution is paused. Thus, if the caret is positioned at the line which has already been executed, the program will be just resumed for further execution because there is no way to roll back to previous breakpoints. This action is especially useful when you have stepped deep into the method sequence and need to step out of several methods at once. If there are breakpoints set for the lines that should be executed before bringing you to the specified line, the debugger will pause at the first encountered breakpoint. Use this action when you need a kind of temporary breakpoint at a specific line, where program execution should not be interrupted.
	Force Run to Cursor `Ctrl+Alt+F9`	Continues the execution until the position of the caret is reached. All breakpoints on the way are ignored.
	Show Execution Point `Alt+F10`	Click this button to highlight the current execution point in the editor and show the corresponding stack frame in the Frames pane.
	Evaluate Expression `Alt+F8`	Click this button to evaluate expressions.