关于python命令中的“-m”选项

按照官方的解释，加-m选项是以模块的方式执行，那么到底是什么意思呢？

首先我们来看下这段简单的测试代码：

#!/usr/bin/python

import sys

print sys.path

我们把这个文件放在/home/hank/下面，然后在根目录下分别执行：

hank@ubuntu:/$ pwd

/

hank@ubuntu:/$ python /home/hank/test.py

['/home/hank', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-x86_64-linux-gnu', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PILcompat', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']

hank@ubuntu:/$ python -m /home/hank/test.py

/usr/bin/python: Import by filename is not supported.

hank@ubuntu:/$ python -m /home/hank/test

['', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-x86_64-linux-gnu', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PILcompat', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']

注意，当我们使用-m选项的时候，一般使用模块名即可，系统自动在后面补齐*.py的后缀。另外，注意sys.path的输出，在加了“-m”选项之后，sys.path包含了当前目录。那么这会带来什么样的效果呢，且看下面的代码：

package1/__init__.py

              mod1.py

package2/__init__.py

               run.py

run.py的代码如下：

#!/usr/bin/python

import sys

from package1 import mod1

print sys.path

分别带“-m”执行和不带“-m”执行run.py脚本，结果如下：

hank@ubuntu:~$ python -m package2/run['', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-x86_64-linux-gnu', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PILcompat', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']

hank@ubuntu:~$ python  package2/run.py  Traceback (most recent call last):  File "package2/run.py", line 3, infrom package1 import mod1

ImportError: No module named package1

可以看到不带“-m”选项执行时，由于sys.path不包含当前目录，所以当执行from package1 import mod1会搜不到package1这个包。