原文

 

多年来，我一直非常高兴地使用jupyter notebook ，主要是使用Python，而且在学术界和业界，它们的流行程度都在不断增长，这是确定无疑的。不过，我确实有些恼火，这就是缺少类似于Eclipse、IntelliJ或VisualStudio代码等其他IDE中提供的一流的可视化调试器。有些人会正确地指出，木星已经支持PDB进行简单的调试，您可以手动和顺序地输入命令来执行诸如检查变量、设置断点等 - 等操作，在调试简单分析时，这可能就足够了。为了提高标准，Pixiedust团队很乐意为木星笔记本介绍第一个(据我们所知)VisualPython调试器

 

 

Editor’s note: PixieDebugger currently only works with classic Jupyter Notebooks; JupyterLab is not yet supported.

 

Introducing PixieDebugger

As advertised, the PixieDebugger is a visual Python debugger built as a PixieApp, and includes a source editor, local variable inspector, console output, the ability to evaluate Python expressions in the current context, breakpoints management, and a toolbar for controlling code execution.

To invoke the PixieDebugger for a specific cell, simply add the %%pixie_debugger magic at the top of the cell and run it.

As an example, let’s consider the following sample code that finds the max value in an array.

 

Note: As a prerequisite, install PixieDust using the following pip command: pip install pixiedust. You’ll also need to import it into its own cell: import pixiedust.

When running the cell, the PixieDebugger will automatically be invoked to break at the first executable line of code.

PixieDebugger in action

Some details to note:

• The toolbar on the top left lets you control the execution flow of your code: resume execution, step over, step into, step out, move current frame one up and one down.
• The source editor shows the current code and highlights the current line being executed. The gutter on the left shows the line numbers and an icon for each line that has a breakpoint installed.
• The variables panel on the right automatically shows the local variables for the current context.
• The console tab shows any output from the current program or the PixieDebugger.
• The Evaluate tab allows you to enter any Python expression and run it to get its value.

Evaluate pane of the PixieDebugger

• The Breakpoints tab displays the list of active breakpoints and lets you add a new one. When you add a new breakpoint, an icon is automatically added to the corresponding line.

Setting breakpoints

There’s also a “run to line” feature, where you can run only a portion of code. You can directly run to a specific line of code by hovering over a line number on the gutter to make the icon appear and clicking it to move the code execution to the targeted line. This can be useful when you have a for loop, and don’t want to step into each part of the loop.

PixieDebugger “run to line” feature

Another optimization you might want to use is the ability to set breakpoints as a directive of the %%pixie_debugger magic, by using the -b argument switch, and specify a list of breakpoints separated by a space. The breakpoints can be either a method name or a line number.

Using our previous example, let’s run the PixieDebugger with 2 breakpoints: one stopping at method find_max and the other at line 9.

Note: Line 9 corresponds to line 7 in the original cell’s code. This is because the PixieDebugger is adding a few lines when running it. You should always use the line number shown in the PixieDebugger editor.

 

The code will now automatically stop at the first breakpoint we’ve set in the magic arguments.

Setting breakpoints in the PixieDebugger

Invoking the PixieDebugger post-mortem (after an exception has happened) is also possible with the line magic %pixie_debugger. (Notice the difference between the cell magic, which has two % symbols, and the line magic, which has only one and no argument.) This is useful to troubleshoot hard-to-reproduce errors.

The following sample code simulates a ZeroDivisionError exception. We then call %pixie_debugger in a separate cell.

Post-Mortem debugging after an exception occurred

Note: When in the debugger, the main thread in the kernel is suspended; therefore, no other code can be executed until the debugging session is done. You will know that it’s safe to execute other cells when the “kernel busy” indicator on the top right of the Notebook page is back to idle.

Using the PixieDebugger to debug PixieApp routes

Where it becomes even more interesting is that the PixieDebugger also works to debug PixieApps. To illustrate how it works, let’s take an example of a simple PixieApp that has one button that calls a route called bad_route to populate a div element. In turn, the bad_route implementation calls bad_method, which triggers a ZeroDivisionError exception.

To debug bad_route, we simply use the debug_route keyword argument with the value “bad_route”. This will trigger the debugger when bad_route is invoked upon clicking the button:

 

Debugging a PixieApp with PixieDebugger

Let’s run this cell and see how the PixieDebugger is triggered when bad_route is invoked. What’s more, the PixieDebugger is actually displayed in the target div the route is supposed to populate.

PixieDebugger invoked to debug a PixieApp route

In case you didn’t specify a route to be debugged and an exception occurs, the PixieApp framework now provides an enhanced traceback with two extra buttons:

• Post-Mortem: Invoke the debugger to do a post-mortem troubleshooting session.
• Debug Route: While post-mortem is only used to inspect local variables, you can use the debug route button to replay the route, stopping at the first executable statement.

Here’s what the new traceback looks like with the sample PixieApp above:

Enhanced traceback for PixieApp with debugging facilities

Bugging out

The new PixieDebugger feature provides a long-awaited visual Python debugger to the Jupyter Notebook ecosystem, which takes data science notebooks one step closer to becoming a true IDE for both data scientists and developers.

The first version will be available starting in PixieDust 1.1.8, and I hope you will give it a try. As always, we look forward to your feedback on how to improve it, either by contributing a pull request or creating issues on the PixieDust GitHub Repo.

From the PixieDust team: Enjoy!

 

 

Jupyter notebook 断点调试快捷键

 

 

表 1. pdb 常用命令

命令	解释
break 或 b 设置断点	设置断点
continue 或 c	继续执行程序,运行到下一个断点
list 或 l	查看当前行的代码段 ，显示断点周围的源代码
step 或 s	进入函数，步进，一步步的执行
return 或 r	执行代码直到从当前函数返回
exit 或 q	中止并退出
next 或 n	执行下一行
pp	打印变量的值
help	帮助