检测Python脚本是从IPython外壳运行还是从命令行运行

Question

有没有办法检测一个Python脚本是从Python或IPython的命令行运行，还是像这样从命令行直接运行，比如用python scrip.py?

我想用这个来设置我的matplotlib环境，根据脚本是怎么运行的来决定是保存图像还是显示图像。当我从命令行运行绘图脚本时，我希望脚本使用一个非标准的matplotlib后端，并用plt.savefig()把图像保存到文件里；但如果我是在IPython的环境中运行，比如用In [1]: run scrip.py，我希望用plt.show()来显示图像。

大概是这样的：

import matplotlib
if run_from_command_line:
    matplotlib.use("non-standard-backend")

import matplotlib.pyplot as plt
if run_from_interactive_shell:
    plt.ion() // Turn on interactive mode in matplotlib

// Do plotting

if run_from_command_line:
    plt.savefig(filename)
else:
    plt.show()

Answer 1

方法 1

在 IPython 中，有一个叫做 __IPYTHON__ 的全局变量。你可以通过检查这个变量是否存在来判断你是否在 IPython 中运行：

try:
    __IPYTHON__
except NameError:
    print "Not in IPython"
else:
    print "In IPython"

方法 2

正如这个讨论所提到的，你还可以在你的脚本中查找 get_ipython 函数，这样不仅可以确认你是否在 IPython 中运行，还能查看 IPython 的配置情况。

方法 3

你还可以使用inspect模块来检查当前的调用栈，看看你是否是在交互式解释器中运行等。

下面是一个示例文件：

# test.py
import inspect

for frame in inspect.stack():
    print frame

当通过命令行运行 python test.py 时，输出结果是：

(<frame object at 0x100378530>, 'test.py', 3, '<module>', ['for frame in inspect.stack():\n'], 0)

当在交互式解释器中使用 execfile 执行时：

>>> execfile( "test.py" )
(<frame object at 0x1003795e0>, 'test.py', 3, '<module>', ['for frame in inspect.stack():\n'], 0)
(<frame object at 0x100379430>, '<stdin>', 1, '<module>', None, None)

在 IPython 中运行时：

In [1]: %run test
(<frame object at 0x1029002a0>, '/Users/ebarr/Scripts/SO/test.py', 3, '<module>', ['for frame in inspect.stack():\n'], 0)
(<frame object at 0x102900020>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/utils/py3compat.py', 224, 'execfile', ['            builtin_mod.execfile(filename, *where)\n'], 0)
(<frame object at 0x101d78e20>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/core/interactiveshell.py', 2537, 'safe_execfile', ['                py3compat.execfile(fname,*where)\n'], 0)
(<frame object at 0x101d78c30>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/core/magics/execution.py', 703, 'run', ['                                       exit_ignore=exit_ignore)\n'], 0)
(<frame object at 0x101d76390>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/core/magics/execution.py', 717, 'run', ['                            run()\n'], 0)
(<frame object at 0x101d61760>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/core/magic.py', 193, '<lambda>', ['        call = lambda f, *a, **k: f(*a, **k)\n'], 0)
(<frame object at 0x101d761a0>, '<string>', 2, 'run', None, None)
(<frame object at 0x101d603e0>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/core/interactiveshell.py', 2126, 'run_line_magic', ['                result = fn(*args,**kwargs)\n'], 0)
(<frame object at 0x101d5f1f0>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/core/interactiveshell.py', 2205, 'magic', ['        return self.run_line_magic(magic_name, magic_arg_s)\n'], 0)
(<frame object at 0x101d75e40>, '<ipython-input-1-59a1e9768ae2>', 1, '<module>', [u"get_ipython().magic(u'run test')\n"], 0)
(<frame object at 0x101d75990>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/core/interactiveshell.py', 2883, 'run_code', ['                exec(code_obj, self.user_global_ns, self.user_ns)\n'], 0)
(<frame object at 0x101d75760>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/core/interactiveshell.py', 2833, 'run_ast_nodes', ['                if self.run_code(code):\n'], 0)
(<frame object at 0x101d71950>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/core/interactiveshell.py', 2741, 'run_cell', ['                                   interactivity=interactivity, compiler=compiler)\n'], 0)
(<frame object at 0x101d6ce10>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/terminal/interactiveshell.py', 567, 'interact', ['                    self.run_cell(source_raw, store_history=True)\n'], 0)
(<frame object at 0x101d6c870>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/terminal/interactiveshell.py', 443, 'mainloop', ['                    self.interact(display_banner=display_banner)\n'], 0)
(<frame object at 0x101716d60>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/terminal/ipapp.py', 371, 'start', ['            self.shell.mainloop()\n'], 0)
(<frame object at 0x1017006f0>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/config/application.py', 563, 'launch_instance', ['        app.start()\n'], 0)
(<frame object at 0x1014fbdd0>, '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/__init__.py', 118, 'start_ipython', ['    return launch_new_instance(argv=argv, **kwargs)\n'], 0)
(<frame object at 0x100378560>, '/Library/Frameworks/Python.framework/Versions/2.7/bin/ipython', 11, '<module>', ['    sys.exit(start_ipython())\n'], 0)