JANAF Thermochemical Tables Wrapper

1.2.1 · active · verified Fri Apr 17

janaf is a Python wrapper for the NIST-JANAF Thermochemical Tables, providing programmatic access to thermodynamic data for various chemical species. The current version is 1.2.1, with releases occurring a few times a year, often including dependency updates and minor feature enhancements.

Common errors

```
ModuleNotFoundError: No module named 'janaf'
```
cause The `janaf` package is not installed in your current Python environment.

fix Install the package using pip: `pip install janaf`
```
AttributeError: 'Table' object has no attribute 'to_xarray'
```
cause You are trying to use the `to_xarray()` method, but the `xarray` optional dependency is not installed.

fix Install `janaf` with the `xarray` extra: `pip install "janaf[xarray]"` or install `xarray` directly: `pip install xarray`.
```
ValueError: No data found for species 'MY_INVALID_SPECIES'
```
cause The species name provided to `janaf.get_table()` does not exactly match an entry in the NIST-JANAF Thermochemical Tables that `janaf` has access to.

fix Verify the exact species name and casing against standard NIST-JANAF nomenclature. For example, use 'H2O' instead of 'WATER'.
```
TypeError: cannot convert float NaN to integer
```
cause After `janaf` v1.1.0, missing data points are no longer imputed and appear as `NaN`. If your downstream code expects non-`NaN` numerical values or attempts to convert `NaN` floats to integers, this error can occur.

fix Explicitly handle `NaN` values in the DataFrame returned by `get_table()`. Use methods like `.dropna()`, `.fillna()`, or ensure type conversions are robust to `NaN`.

Warnings

breaking Python 3.8 support was dropped in `janaf` v1.2.1. If you are using Python 3.8 or older, you must either upgrade your Python version or pin `janaf` to a version older than 1.2.1.
Fix: Upgrade Python to 3.9+ or use `pip install 'janaf<1.2.1'`.
breaking As of v1.1.0, `janaf` no longer performs runtime imputation of missing data points (e.g., for `cp0/R`). If your code relied on these estimated values for certain species or temperature ranges, you might now encounter `NaN` values where data was previously provided.
Fix: Update your code to explicitly handle `NaN` values (e.g., `dropna()`, `fillna()`, or manual interpolation) or ensure your data sources cover the full range of interest. Alternatively, pin `janaf` to `<1.1.0` if this imputation behavior is critical.
gotcha The `Table.to_xarray()` method requires the optional `xarray` dependency to be installed. If `xarray` is not installed, calling this method will result in an `AttributeError`.
Fix: Install `janaf` with the `xarray` extra: `pip install "janaf[xarray]"` or install `xarray` separately: `pip install xarray`.

Install

pip install janaf Standard Install
pip install "janaf[xarray]" Install with xarray support

Imports

get_table
```
from janaf import get_table
```
constants
```
from janaf import constants
```

Quickstart

This quickstart demonstrates how to fetch thermochemical data for a species (e.g., H2O) using `janaf.get_table()` and access the data as a pandas DataFrame. It also shows how to retrieve specific property values.

from janaf import get_table

# Get thermochemical data for Water
water_table = get_table("H2O")

# Access data as a pandas DataFrame
print("\nWater Table (first 5 rows):\n", water_table.df.head())

# Access specific properties
print(f"\nEnthalpy (H) at 298.15 K: {water_table.df.loc[298.15, 'H/RT']} RT")

# Get data for another species
oxygen_table = get_table("O2")
print("\nOxygen Table (first 5 rows):\n", oxygen_table.df.head())

view raw JSON →