How to execute python program in python shell in Linux importing a special environment

Question

I use a piece of astrophysical software called AMUSE, which uses python command line. I have got the binary release that imports amuse in terminal. Now if I want to run a saved python program in any directory, how do I call it?

Previously I used in terminal

python first.py 
pwd=secret;database=master;uid=sa;server=mpilgrim

The first.py looks like this

def buildConnectionString(params):
    """Build a connection string from a dictionary of parameters.

    Returns string."""
    return ";".join(["%s=%s" % (k, v) for k, v in params.items()])

if __name__ == "__main__":
    myParams = {"server":"mpilgrim", \
                "database":"master", \
                "uid":"sa", \
                "pwd":"secret" \
                }
    print buildConnectionString(myParams)

And my codes worked, now I am in python shell

 Python 2.7.2 (default, Dec 19 2012, 16:09:14)  [GCC 4.4.6] on linux2
Type "help", "copyright", "credits" or "license" for more information.
 >>> import amuse
 >>>

So if I want the output of any code here, how do I proceed?

I had a program saved in my Pictures/practicepython directory, how can I call that particular .py files in python shell?

with import command, I am getting this error msg

Python 2.7.2 (default, Dec 19 2012, 16:09:14) 
[GCC 4.4.6] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import amuse
>>> import first
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named first
>>>

Kevin · Accepted Answer · 2014-12-03 15:12:24Z

2

If a Python module is designed properly, it will have a few lines like this, usually near the end of the module:

if __name__ == '__main__':
    main()  # or some other code here

Assuming first.py looks like that, you can just call the main() function:

>>> import first
>>> first.main()

Note that main() might raise SystemExit, which will cause the REPL to exit. If this matters to you, you can catch it with a try block:

>>> import first
>>> try:
...     first.main()
... except SystemExit:
...     pass

Unfortunately, some modules don't have a proper main() function (or anything similar), and simply put all their top-level code in the if. In that case, there's no straightforward way to run the module from the REPL, short of copying the code.

If a Python module is not designed properly at all, it will run as soon as you import it. This is usually considered a Bad Thing because it makes it harder for others to use the module programmatically (e.g. calling the module's functions, instantiating its classes, etc.).

answered Dec 3, 2014 at 15:12

Kevin

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4 Comments

Tazkera Haque Trina Over a year ago

the first.py is updated with my question and its well built I see. but if I follow your instruction it gives me error in the first place, which I also updated in the post, can You please check and tell me the how to fix?

Kevin Over a year ago

@TazkeraHaqueTrina: You need to be in the same directory as first.py, or you need to install (copy) first.py into one of the directories listed in sys.path.

Tazkera Haque Trina Over a year ago

can you please instruct me how to do that? I did not understand how to make copy files and the sys.path.

Kevin Over a year ago

@Tazkera: The easiest option is to copy first.py into the current directory. At the Unix command prompt, this is done with cp -t . path/to/first.py. See cp(1) or type man cp at the command line for more details.

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