理解python -c||python -m interpreter run scripts

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缘起

refer2中使用到:

python -c 'import site; print(site.getsitepackages())'
python3 -c 'import sysconfig; print(sysconfig.get_paths()["purelib"])'

-c -m are both command-line[refer1] options.

When invoking Python ,you may specify any of these options:

python [-bBdEhiIOqsSuvVWx?] [-c command | -m module-name | script | - ] [args]

Using the Python Interpreter

The Python interpreter is usually installed as /usr/local/bin/python3.9 on those machines where it is avaiable; putting /usr/local/bin in your Unix shell’s search path makes it possible to start it by typing the command:
```
python3.9
```
to the shell.

Redirecting the output

python hello.py > output.txt # rather than to the stdout,known as stram redirection. It will create or replace output.txt
python hello.py >> output.txt # add the output to the file

Using python module -m module
```
python -m <module-name>
python -m hello
# not
python -m hello.py
```
The -m option searches sys.path for the module name and runs its content as _main_

对于功能单一的代码，就可以用这样的方式，而不用写复杂的argparses
Execute the Python statements -c command

It executes the Python statements given as command.

Here command may contain multiple statements separated by newlines.

And leading whitespace is significant.

If the option is given, the first element of sys.argv will be “-c” and the current directory will be added to the start of sys.path(allowing modules in that directory to be imported as top level modules).
import runs the code as its final stop

It just do the “run” work once, after the first import, successive import executions do nothing.
importlib module
exec(open('hello.py').read())
Stop running

Control-D Unix;

Control-Z Windows;
总结
python -m or python -c both run python scripts using the interpreter.

关于python -m和python -c的用法，在网上搜索很难发现什么资料，后来才突然意识到，想要学习它们，最好的资料是它们自己的帮助文档：
```
python -h
```
References