如何在 jupyter 中定义自定义魔法？

Question

我正在使用 Ubuntu 14.04 LTS 和 Anaconda python 安装：

Python 3.5.1 :: Anaconda 2.4.1 (64-bit)

我正在尝试使用 this recipe 在我的 ipython 笔记本中启用 C++ 交互式编译：

import IPython.core.magic as ipym

@ipym.magics_class
class CppMagics(ipym.Magics):
    @ipym.cell_magic
    def cpp(self, line, cell=None):
        """Compile, execute C++ code, and return the standard output."""
        # Define the source and executable filenames.
        source_filename = 'temp.cpp'
        program_filename = 'temp.exe'
        # Write the code contained in the cell to the C++ file.
        with open(source_filename, 'w') as f:
            f.write(cell)
        # Compile the C++ code into an executable.
        compile = self.shell.getoutput("g++ {0:s} -o {1:s}".format(
            source_filename, program_filename))
        # Execute the executable and return the output.
        output = self.shell.getoutput(program_filename)
        return output

def load_ipython_extension(ipython):
    ipython.register_magics(CppMagics)

当我用 :

执行一个单元格时，我是用 ipython notebok 还是 jupyter notebook 启动我的笔记本（我相信第一个别名是第二个别名）

%load_ext cppmagic

我收到以下错误：

---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-1-7b90c7a2b808> in <module>()
----> 1 get_ipython().magic('load_ext cppmagic')

/home/norah/anaconda3/lib/python3.5/site-packages/IPython/core/interactiveshell.py in magic(self, arg_s)
   2334         magic_name, _, magic_arg_s = arg_s.partition(' ')
   2335         magic_name = magic_name.lstrip(prefilter.ESC_MAGIC)
-> 2336         return self.run_line_magic(magic_name, magic_arg_s)
   2337 
   2338     #-------------------------------------------------------------------------

/home/norah/anaconda3/lib/python3.5/site-packages/IPython/core/interactiveshell.py in run_line_magic(self, magic_name, line)
   2255                 kwargs['local_ns'] = sys._getframe(stack_depth).f_locals
   2256             with self.builtin_trap:
-> 2257                 result = fn(*args,**kwargs)
   2258             return result
   2259 

/home/norah/anaconda3/lib/python3.5/site-packages/IPython/core/magics/extension.py in load_ext(self, module_str)

/home/norah/anaconda3/lib/python3.5/site-packages/IPython/core/magic.py in <lambda>(f, *a, **k)
    191     # but it's overkill for just that one bit of state.
    192     def magic_deco(arg):
--> 193         call = lambda f, *a, **k: f(*a, **k)
    194 
    195         if callable(arg):

/home/norah/anaconda3/lib/python3.5/site-packages/IPython/core/magics/extension.py in load_ext(self, module_str)
     64         if not module_str:
     65             raise UsageError('Missing module name.')
---> 66         res = self.shell.extension_manager.load_extension(module_str)
     67 
     68         if res == 'already loaded':

/home/norah/anaconda3/lib/python3.5/site-packages/IPython/core/extensions.py in load_extension(self, module_str)
     87             if module_str not in sys.modules:
     88                 with prepended_to_syspath(self.ipython_extension_dir):
---> 89                     __import__(module_str)
     90             mod = sys.modules[module_str]
     91             if self._call_load_ipython_extension(mod):

ImportError: No module named 'cppmagic'

食谱中的代码似乎与 the official docs 一致（都使用 IPython.core.magic.magics_class）我已将我的 cppmagic.py 放在以下目录中

~/.ipython/profile_default/startup

让它在笔记本电脑启动时自动加载，但我无法感受到它的魔力。有人可以帮忙吗？

Answer 1

这里有两个独立的东西：

启动文件是~/.ipython/profile_[name]/startup中的脚本，作为启动IPython的一部分执行。在第一个 In[1] 提示之前，他们被视为您 %run 每个人。无法导入启动文件，因为它们不在 sys.path.
extensions 是 Python 可以导入并定义 load_ipython_extension 函数的模块。您可以将扩展放在 ~/.ipython/extensions 中，它们将是可导入的，或者您可以将它们作为常规包安装 pip.

第一个修复是将您的 cppmagics 移动到 ~/.ipython/extensions 或某个 site-packages 目录，以便它可以导入。

如果您真的希望魔法总是注册（而不是调用 %load_ext cppmagic），您可以将其保留为启动文件并在脚本末尾注册魔法，而不是 def load_ipython_extension :

if __name__ == '__main__':
    from IPython import get_ipython
    get_ipython().register_magics(CppMagics)

如何在 jupyter 中定义自定义魔法？

How do I define custom magics in jupyter?

python

ipython

ipython-notebook

ipython-magic

jupyter-notebook