atct - Pythonic ATcT v1 API Client

A comprehensive Python client for the ATcT v1 API with advanced reaction enthalpy calculation capabilities.

Features

• Complete v1 API coverage - all endpoints implemented with proper error handling
• Reaction calculations - advanced uncertainty propagation with multiple methods
• Minimal dependencies - works with only Python standard library and httpx
• Optional enhancements - numpy for advanced calculations, pandas for DataFrames
• Dual import support - use from atct.api import ... or from atct import ...
• Robust error handling - comprehensive exception mapping and retry logic
• Environment flexibility - local/production URL switching

Installation

# Basic installation (httpx only)
pip install atct

# With pandas support for DataFrames
pip install atct[pandas]

# With numpy support for advanced reaction calculations
pip install atct[numpy]

# With both pandas and numpy
pip install atct[all]

Quickstart

from atct.api import get_species, search_species, calculate_reaction_enthalpy

# Get species data
species = get_species("67-56-1*0")  # Methanol
print(f"{species.name}: {species.delta_h_298k} ± {species.delta_h_298k_uncertainty} kJ/mol")

# Search for species
results = search_species("methanol", limit=5)
for item in results.items:
    print(f"{item.name} ({item.atct_id})")

# Calculate reaction enthalpy (298.15K values, default)
species_data = {
    '67-56-1*0': -1.0,    # CH3OH (reactant)
    '7727-37-9*0': -1.5,  # O2 (reactant) 
    '124-38-9*0': 1.0,    # CO2 (product)
    '7732-18-5*0': 2.0    # H2O (product)
}
result_298k = calculate_reaction_enthalpy(species_data, 'covariance')
print(f"298.15K reaction enthalpy: {result_298k}")

# Calculate reaction enthalpy with 0K values (conventional method only, fails if 0K not available for any species)
try:
    result_0k = calculate_reaction_enthalpy(species_data, 'conventional', use_0k=True)
    print(f"0K reaction enthalpy: {result_0k}")
except ValueError as e:
    print(f"Cannot use 0K values: {e}")

API Functions

Species Data

• get_species(atctid, expand_xyz=False) - Get species by ATcT ID
• search_species(q, limit=50, offset=0) - Search species by name or formula
• get_species_by_smiles(smiles) - Get species by SMILES string
• get_species_by_casrn(casrn) - Get species by CAS Registry Number
• get_species_by_inchi(inchi) - Get species by InChI
• get_species_by_formula(formula, phase=None, descriptor=None) - Get species by formula
• get_species_by_name(name) - Get species by name

Covariance Data

• get_species_covariance_by_atctid(a_atctid, b_atctid) - Get 2x2 covariance matrix
• get_species_covariance_by_ids(a_id, b_id) - Get covariance by numeric IDs

Reaction Calculations

• calculate_reaction_enthalpy(species_data, method, use_0k=False) - Calculate reaction enthalpy
  • use_0k=True: Use 0K enthalpy values with conventional method only (fails if not available for any species)
  • use_0k=False: Use 298.15K enthalpy values (default)
• create_reaction_calculator(species_data, use_0k=False) - Create reaction calculator

Note: The covariance method requires numpy (pip install atct[numpy]) and should only be used with 298.15K values. The conventional method works without external dependencies and is used for 0K calculations. A warning will be issued if covariance method is used with 0K values, as the covariance matrix is only valid at 298.15K (the temperature the Thermochemical Network was solved at).

Utility

• healthcheck() - Check API health status
• as_dataframe(items) - Convert results to pandas DataFrame

Data Models

Species

@dataclass
class Species:
    atct_tn_version: Optional[str]
    atct_id: str
    name: Optional[str]
    formula: Optional[str]
    delta_h_0k: Optional[str]
    delta_h_298k: Optional[str]
    delta_h_298k_uncertainty: Optional[str]
    unit: Optional[str]
    mass: Optional[str]
    mass_uncertainty: Optional[str]
    smiles: Optional[str]
    casrn: Optional[str]
    charge: Optional[int]
    xyz: Optional[Union[str, List[str]]]

Covariance2x2

@dataclass
class Covariance2x2:
    labels: List[str]
    units: str
    matrix: List[List[float]]  # 2x2 matrix

Reaction Models

@dataclass
class ReactionSpecies:
    species: Species
    stoichiometry: float

@dataclass
class ReactionResult:
    delta_h: float
    uncertainty: float
    method: str
    units: str = "kJ/mol"

Error Handling

The package provides specific exceptions for different error conditions:

from atct import ATCTError, NotFound, BadRequest, Unauthorized, ServerError, NetworkError

try:
    species = get_species("invalid-id")
except NotFound:
    print("Species not found")
except NetworkError:
    print("Network connection failed")
except ATCTError as e:
    print(f"API error: {e}")

Configuration

Set environment variables to configure the client:

• ATCT_API_BASE_URL (default: https://atct.anl.gov/api/v1) - API endpoint
• ATCT_API_KEY (optional, for authenticated requests)
• ATCT_TIMEOUT_S (default: 10 seconds)
• ATCT_RETRIES (default: 3 retry attempts)
• ATCT_USER_AGENT (default: atct/1.0.0)

The client uses the v1 API exclusively.

Development

# Install in editable mode
pip install -e .

# Run tests
pytest -q

# Run examples
python examples/example_usage.py
python examples/example_reaction_calculations.py

Examples

See the examples/ directory for comprehensive usage examples:

• example_usage.py - Basic API functionality
• example_reaction_calculations.py - Advanced reaction calculations

v1 API Endpoints

This package targets the ATcT v1 API exclusively:

• GET /api/v1/health - Health check
• GET /api/v1/species/get/by-atctid/ - Get species by ATcT ID
• GET /api/v1/species/search/ - Search species
• GET /api/v1/species/get/by-smiles/ - Get species by SMILES
• GET /api/v1/species/get/by-casrn/ - Get species by CASRN
• GET /api/v1/species/get/by-inchi/ - Get species by InChI
• GET /api/v1/species/get/by-formula/ - Get species by formula
• GET /api/v1/species/get/by-name/ - Get species by name
• GET /api/v1/covariance/species/ - Get covariance matrices