Invoke AMPL from Python

[Vaibhav Rungta]

Hello Folks,

I want to invoke an AMPL script from Python.

The AMPL folder I am using has ampl.exe, minos.exe, the run and mod files.

The python program has been saved at other location.

I checked the support available online. It suggests use of "ampl name_of_run_file.run" with subprocess.call but I am getting an error when I include path along with file name.

For once I tried saving the python file in same folder as the run file and os.startfile. That works. But I wish to keep the python file in separate folder and call the ampl from there. Please suggest.

P.S: I am a beginner with Python. Still learning.

Regards,

Vaibhav Rungta

Graduate Student - Industrial and Systems Engineering

Graduate Assistant - Toyota Production Systems Lab

Research Assistant - University Transport Research Center

585-754-7133

[Filipe Brandão]

Hi Vaibhav,

If you set the environment variable ampl_include (with os.environ["ampl_include"] = "path/to/folder"), AMPL will search for files in the other folder too and the script should work.

from __future__ import print_function
from subprocess import Popen, PIPE
import os
os.environ["ampl_include"] = "models/"

process = Popen(["ampl", "models/model.run"], stdin=PIPE, stdout=PIPE)
for line in process.stdout:
    print(line, end="")

By the way, a Python API for AMPL is planned to be included in the next released of the AMPL API.

Best regards,
Filipe

[Vaibhav Rungta]

Hello Filipe,

I'll try the steps you have recommended and get back to you in case of any query. 

Thank you for the much needed help :)

Regards,

Vaibhav Rungta

Graduate Student - Industrial and Systems Engineering

Graduate Assistant - Toyota Production Systems Lab

Research Assistant - University Transport Research Center

585-754-7133

[Filipe Brandão]

Hi Vaibhav,

Since you have spaces in the path, you may need to use raw strings instead (i.e., r"C:/Users/Public/Music/Sample Music/AMPL/ampl_mswin64/" instead of "C:/Users/Public/Music/Sample Music/AMPL/ampl_mswin64/").

Best regards,

Filipe

On Fri, Apr 21, 2017 at 5:10 PM, Vaibhav Rungta <vr2...@rit.edu> wrote:

Hello Filipe,

I used the code shared above and declared environment variable.

I am still getting an error (screenshot attached herewith). I might have done something wrong. I'll appreciate your help. Thanks.

Regards,

Vaibhav Rungta

Graduate Student - Industrial and Systems Engineering

Graduate Assistant - Toyota Production Systems Lab

Research Assistant - University Transport Research Center

585-754-7133

[Vaibhav Rungta]

Hello Filipe,

I used the code shared above and declared environment variable.

I am still getting an error (screenshot attached herewith). I might have done something wrong. I'll appreciate your help. Thanks.

Regards,

Vaibhav Rungta

Graduate Student - Industrial and Systems Engineering

Graduate Assistant - Toyota Production Systems Lab

Research Assistant - University Transport Research Center

585-754-7133

On Fri, Apr 21, 2017 at 9:37 AM, Vaibhav Rungta <vr2...@g.rit.edu> wrote:

[Vaibhav Rungta]

Hello Filipe,

I tried your your recommendation. I couldn't get it to work.

Therefore, I moved all the AMPL files to the folder which has Python files. It worked for sometime but for some reason (I don't know why) the Python program giving an error of "data file not found", again. Python file attached here with.

- Creates .dat file through Python. Similar to writing a text file. The .dat file gets overwritten and is called in .run file.

- I have also included a 3 line script in the .run file to write output (just capturing final speed and acceleration time) to a .txt file.

- Reads the .txt file from Python and saves the values for use in SUMO.

I can't figure out what's wrong. I deleted the old .exe files and extracted all the files again in the same folder but I still can't get it to work. Screen shot attached.

Regards,

Vaibhav Rungta

Graduate Student - Industrial and Systems Engineering

Graduate Assistant - Toyota Production Systems Lab

Research Assistant - University Transport Research Center

585-754-7133

[Filipe Brandão]

Hi Vaibhav,

The only problem that I noticed with your code was that subprocess.call("ampl deccrun_new.run") should be replaced subprocess.call(["ampl", "deccrun_new.run"]) (https://docs.python.org/2/library/subprocess.html).

Regarding the screen-shot, could you please run "cd;" in AMPL after that error in order to check the current working of AMPL?

Best regards,
Filipe

[Vaibhav Rungta]

Hello Filipe,

I checked the ampl.exe with cd; command. It shows the existing work directory where all the other .mod, .dat and .run files are placed.

I also moved the files to another folder and have deleted the ampl files and copied again. Still the same error. Attached herewith are some screenshots which might provide  more information.

You have been very supportive. 

I have used ampl in past but I never came across this issue. I have tried multiple things but it even the most basic operations aren't working. I'll check for Python once I fix this. Kindly suggest.

Regards,

Vaibhav Rungta

Graduate Student - Industrial and Systems Engineering

Graduate Assistant - Toyota Production Systems Lab

Research Assistant - University Transport Research Center

585-754-7133

[AMPL Support]

Hi Vaibhav,

On your second slide, it appears that your file is named deccrun_new1.run but you have given the command "include decc_new1.run" -- that would explain why the file can't be found.  It is not immediately clear why, on the first slide, data_veh.dat is not being found, so we suggest some more troubleshooting steps.

First, move the folder ampl.mswin64 (shown in the second slide) to your desktop, and try running AMPL from there.  If you still have a problem, send us again the screenshots showing the output of cd and the error, and a screenshot of the folder display -- it will be a normal Windows folder display rather than the Music Library display that we are currently seeing.  Also attach the model, data, and run files that you are trying to use in your test.

AMPL Support Services
sup...@ampl.com

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[John]

Hi!!!

I am a bit late for the conversation but I have got the same problem: dat afile is not found.

As I see python manages to run AMPL.exe and read mydatafile.run

but when running * .run file the data file is not found.

I use thefollowing code in python:

process = Popen([pathToamplExe, patheToRunFile], stdin=PIPE, stdout=PIPE, shell=True)

for line in process.stdout:
   print(line, end="")

   print("\n")

The message is:

b'C:\\Users\\yauhenik\\OneDrive\\Python\\Combinator_Web\\CombinatorHybridWork\\CombinatorHybrid.run, line 125 (offset 7655):\r\n'

b'\tCan\'t find  file "CombinatorOriginalHybrid.dat"\r\n'

b'context:  data  >>> CombinatorOriginalHybrid.dat; <<< \r\r\n'

вторник, 2 мая 2017 г., 5:06:23 UTC+2 пользователь AMPL Support написал:

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[AMPL Google Group]

You missed the line that sets the environment variable ampl_include to the directory containing the model files. The following should work:

from subprocess import Popen, PIPE

import os

pathToamplExe = r'C:/path/to/ampl'
patheToRunFile = r'C:/path/to/models/file.run'

os.environ["ampl_include"] = r'C:/path/to/models/'
process = Popen([pathToamplExe, patheToRunFile], stdin=PIPE, stdout=PIPE)

for line in process.stdout:
print(line, end="")

print("\n")


Please note however, that there is a Python API for AMPL called amplpy. You may want to use amplpy instead (see, e.g., https://amplpy.readthedocs.io/en/latest/quick-start.html) as it will simplify the interaction between Python and AMPL.

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Filipe Brandão
am...@googlegroups.com

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