ChemApp for Python is a software library for thermodynamic calculations. GTT-Technologies provides different editions of ChemApp for Python. The Light edition is free of charge and a good way to try out its features, although it has some limitations (e.g., max. 50 constituents, 3 components, and 5 mixture phases). Importantly, the Light edition works only with unencrypted .dat database files. If you need to work with encrypted .cst files, you need a paid license.

Because it is free and requires no dongle, ChemApp for Python – Light is perfect for getting started. Below you will find two ways to install and run it on your computer.

Option 1: Install with Anaconda

If you already use Anaconda (a popular Python distribution), follow the steps below.

1. Download the ChemApp Light package from:
   https://python.gtt-technologies.de/packages/light/
2. Open the Anaconda Prompt and install the downloaded wheel file. For example, if you downloaded:

pip install chemapplight-4.1.1-cp311-cp311-win_amd64.whl

1. Verify installation by opening Python and typing:

import chemapplight

Option 2: Install with uv

uv is a new, fast Python package installer (an alternative to pip). We recommend you to try uv and follow these steps:

1. Install uv by following instructions on its homepage.
2. Download the ChemApp Light package from the GTT website (same link as above).
3. Install the downloaded wheel file with uv:

uv pip install chemapplight-4.1.1-cp311-cp311-win_amd64.whl

1. Test the installation in Python:

import chemapplight

First Example Script

Once installed, you can try the following example to check that ChemApp for Python Light is working:

# Import the ChemApp for Python friendly module.
from chemapplight.friendly import ThermochemicalSystem as cats
from chemapplight.friendly import Units as cau

# Determine the data file path.
from pathlib import Path
import chemapplight
data_dir = Path(chemapplight.__file__).parents[0] / 'data'

# Suggestion: For this program to be flexible, add code that asks for
# the name of the data file instead.
fname = str(data_dir / 'cosi.dat')

# Use the cats.load() function to initialise ChemApp for Python,
# and load, read, and close the 'cosi.dat' (system C-O-Si) data file.
cats.load(fname)
cau.set()  # set units to default values.

print(f'\nContents of data file {fname}:')

# **********************************************************************
# Information on system components.
# **********************************************************************

# Get the number of system components.
nscom = cats.get_count_scs()
print(f'Number of system components: {nscom}')

# Print the names of all system components.
scname = cats.get_str_scs()
print(scname)

# **********************************************************************
# Information on phases.
# **********************************************************************

# Get the number of phases.
nphase = cats.get_count_phs()
print(f'Number of phases: {nphase}')

# Print the names of all phases, the associated model, and the number of
# phase constituents, if it is a mixture phase.
print(cats.get_str_phs())

That’s it! You now have ChemApp Light running on your computer. From here, you can start exploring thermodynamic calculations and databases. ChemApp for Python also comes with an examples directory, which contains ready-to-run scripts demonstrating common tasks such as reading database files, initializing sessions, and performing basic calculations.

These examples are a great starting point if you are new to ChemApp, since you can run them directly and then modify them to fit your own needs. You can find detailed explanations of these example scripts in the official documentation.