AMPL Python API

0.16.0 verified Mon Apr 27 auth: no python

amplpy is the official Python API for AMPL, a powerful algebraic modeling language for optimization. Version 0.16.0 provides a Pythonic interface to define models, solve them with AMPL's solvers, and manipulate results. It is maintained by AMPL Inc. and follows a regular release cadence aligned with AMPL updates.

pip install amplpy

Common errors

error ModuleNotFoundError: No module named 'amplpy' ↓

cause amplpy is not installed, or installed in a different Python environment.

fix

Run pip install amplpy in the correct environment (e.g., virtualenv).

error RuntimeError: AMPL executable not found. Please set the AMPL path ↓

cause AMPL is not installed or not in PATH, and amplpy cannot locate the AMPL executable.

fix

Set the AMPL path via environment variable AMPLBIN or pass Environment(ampl_bin='/path/to/ampl') to the AMPL constructor.

error TypeError: No matching signature found ↓

cause Using numpy or pandas data types that are not supported by AMPL's C++ interface; often due to using pandas DataFrames with non-string column names.

fix

Convert column names to strings and ensure data types are basic (int, float, str).

Warnings

breaking In amplpy 0.13.0 and later, the `amplpy.AMPL` constructor no longer accepts `ampl_bin` or `format` arguments; use `Environment` to set AMPL path. ↓

fix Use `Environment(ampl_bin='/path/to/ampl')` and pass to `AMPL(environment=env)`.

gotcha When using AMPL DataFrame with pandas DataFrames, the column names may be automatically converted to strings; mixing types can cause silent data loss. ↓

fix Ensure all column names in pandas DataFrames are strings before converting to AMPL DataFrame.

deprecated The method `getData(name)` is deprecated in favor of `get_data(name)` (underscore convention) since version 0.12.0. ↓

fix Replace `getData('x')` with `get_data('x')`.

Imports

AMPL
wrong
```
import amplpy
amplpy.AMPL()
```
correct
```
from amplpy import AMPL
```
Namespace import unnecessary; direct import is standard
DataFrame
wrong
```
from pandas import DataFrame
```
correct
```
from amplpy import DataFrame
```
AMPL DataFrame is separate from pandas DataFrame; using pandas will cause errors
Environment
```
from amplpy import Environment
```

Quickstart

Create an AMPL instance, evaluate a simple model, solve it, and print the objective value.

from amplpy import AMPL, DataFrame
ampl = AMPL()
ampl.eval('var x; maximize obj: x; subject to c: x <= 1;')
ampl.solve()
print('Objective:', ampl.getValue('obj'))