Question: The intended functionality for the code I'm working on is to be able to load in molecules to a two-player game at runtime, and I've largely implemented a good chunk of the physics. I'm wondering if the functionality to look up a specific class type can be accessed in python for the part of the project I'm currently working on. I'm getting integer values from a class function in an imported library (chempy), and the function returns a dictionary of integers to represent which elements are present in a chemical formula, and in what quantity. I've got my own classes for element objects, and I'm trying to build a function which will take this dictionary of integers and construct the appropriate objects. For example, I might call it with the argument = {1:2,8:1} to signify water, because the chempy Substance.composition() method returns this value. My initial thought was that I should just have a list of the elements in the range that I'm intending to implement models of, such that the dictionary keys can be used to index the array. However, I'm not sure how to implement a list of class types, as opposed to pre-loaded objects. I'm imagining something like this: elements = [Hydrogen,Helium,Lithium,Beryllium,Boron,Carbon,Nitrogen,Oxygen]. I'm left wondering how to call a new object of instance elements[i]() (??) where i is a dictionary key from the chempy function's return value. Is any of this valid code? I can't find related documentation online, which makes me wonder if this functionality is accessed through different means, or even really feasible in this language?

Answer: Yes, this is absolutely valid and feasible in Python! You're on the right track. In Python, classes are first-class objects, meaning you can store them in lists, dictionaries, and variables, then call them to create instances. In your case, I recommend the Factory Pattern because it's Extensible, Error-safe, Game-friendly, and Clean. See in action Note: Check the comments, where and how it creates the class instance based on the list, dictionary, or factory lookup. from abc import ABC, abstractmethod from typing import Dict, List, Type class Element(ABC): """Base class for all chemical elements""" def __init__(self, quantity: int = 1): self.quantity = quantity self.atomic_number = self.get_atomic_number() self.symbol = self.get_symbol() self.name = self.get_name() @abstractmethod def get_atomic_number(self) -> int: pass @abstractmethod def get_symbol(self) -> str: pass @abstractmethod def get_name(self) -> str: pass def __repr__(self): return f"{self.__class__.__name__}(quantity={self.quantity})" class Hydrogen(Element): def get_atomic_number(self) -> int: return 1 def get_symbol(self) -> str: return "H" def get_name(self) -> str: return "Hydrogen" class Helium(Element): def get_atomic_number(self) -> int: return 2 def get_symbol(self) -> str: return "He" def get_name(self) -> str: return "Helium" class Lithium(Element): def get_atomic_number(self) -> int: return 3 def get_symbol(self) -> str: return "Li" def get_name(self) -> str: return "Lithium" # SOLUTION 1: List-based approach (your original idea) def create_molecule_list_approach(composition: Dict[int, int]) -> List[Element]: """list-based element lookup""" # List of element classes indexed by atomic number (0 is unused) elements = [ None, # 0 - placeholder Hydrogen, # 1 Helium, # 2 Lithium, # 3 ] molecule = [] for atomic_number, quantity in composition.items(): if atomic_number < len(elements) and elements[atomic_number] is not None: # elements[atomic_number] is a CLASS, calling it creates an INSTANCE element_instance = elements[atomic_number](quantity) molecule.append(element_instance) else: print(f"Warning: Element {atomic_number} not implemented") return molecule # SOLUTION 2: Dictionary-based approach (more flexible) def create_molecule_dict_approach(composition: Dict[int, int]) -> List[Element]: """dictionary-based element lookup""" element_classes = { 1: Hydrogen, 2: Helium, 3: Lithium, } molecule = [] for atomic_number, quantity in composition.items(): if atomic_number in element_classes: ElementClass = element_classes[atomic_number] # elements[atomic_number] is a CLASS a class element_instance = ElementClass(quantity) # This creates an instance molecule.append(element_instance) else: print(f"Warning: Element {atomic_number} not implemented") return molecule # SOLUTION 3: Factory Pattern (recommended for games) class ElementFactory: """Factory class for creating element instances""" def __init__(self): self._elements = { 1: Hydrogen, 2: Helium, 3: Lithium, } def create_molecule(self, composition: Dict[int, int]) -> List[Element]: """Create a molecule from composition dictionary""" molecule = [] for atomic_number, quantity in composition.items(): if atomic_number in self._elements: ElementClass = self._elements[atomic_number] element = ElementClass(quantity) molecule.append(element) else: print(f"Warning: Element {atomic_number} not supported") return molecule def main(): # Example compositions from chempy hydrogen_gas = {1: 2} # H2 lithium_hydride = {3: 1, 1: 1} # LiH print("=== List Approach ===") h2_list = create_molecule_list_approach(hydrogen_gas) lih_list = create_molecule_list_approach(lithium_hydride) print(f"H2: {h2_list}") print(f"LiH: {lih_list}") print("\n=== Dictionary Approach ===") h2_dict = create_molecule_dict_approach(hydrogen_gas) lih_dict = create_molecule_dict_approach(lithium_hydride) print(f"H2: {h2_dict}") print(f"LiH: {lih_dict}") print("\n=== Factory Approach (Recommended) ===") factory = ElementFactory() h2_factory = factory.create_molecule(hydrogen_gas) lih_factory = factory.create_molecule(lithium_hydride) print(f"H2: {h2_factory}") print(f"LiH: {lih_factory}") if __name__ == "__main__": main() # Your Integration with chempy def integrate_with_chempy(): """How to use this with chempy in your game""" # Simulated chempy output (replace with actual chempy code) # from chempy import Substance # composition = Substance.from_formula('H2').composition() composition = {1: 2} # What chempy returns for H2 factory = ElementFactory() molecule = factory.create_molecule(composition) print(f"\nChempy integration example:") print(f"Composition: {composition}") print(f"Molecule: {molecule}") # Use in your game physics for element in molecule: print(f"- {element.name}: {element.quantity} atoms") integrate_with_chempy()