symbols

net.symbols

NetworkSymbols instance owning the network's canonical SymPy symbols, density expressions, introspection sets and symbol standardization.

Fixed symbols (class attributes — also usable as NetworkSymbols.<name> without a network)

Attribute	Symbol	Meaning
`tgas`	`tgas`	Gas temperature [K]
`tdust`	`tdust`	Dust temperature [K]
`av`	`av`	Visual extinction [mag]
`crate`	`crate`	Cosmic-ray ionisation rate [s⁻¹]
`chi`	`chi`	UV field scaling
`chi_pe`	`chi_pe`	Photoelectric-band field (placeholder)
`zd`	`Zd`	Grain charge
`vdisp`	`vdisp`	Velocity dispersion [cm s⁻¹]
`photorates`	`photorates`	Photo-rate placeholder function

ncol(name) → Symbol(f"ncol_{name}") (column density).

Densities (cached)

Attribute	Type	Description
`ndens`	`IndexedBase`	`nden[i]` = number density of species i
`ntot`	`sympy.Expr`	`Σ_i nden[i]`
`rho`	`sympy.Expr`	`Σ_i m_i · nden[i]`
`n_hnuc`	`sympy.Expr`	Hydrogen-nuclei density (`n_H_nuc` token)
`element_sum(element)`	`Expr \\| None`	Nucleus density of element; `None` if absent

Introspection (cached frozenset, filled after loading)

Attribute	Description
`variables`	Free symbols across rates and energy/radiation terms
`interp_functions`	Names of `interp` functions
`undefined_functions`	Names of other undefined functions

Methods

free_symbols(expr) — free symbols of expr, excluding nden entries.

standardize(expr) — replace ntot, n_X, n_e, n_X_nuc, rc_N and chi_pe with their network expressions (names are case-insensitive).

log_summary() — log the network's variables, interpolation and undefined functions (called once when the network is loaded).

net = Network("networks/h_photoionization/h_photo.jet")

net.symbols.ntot            # nden[0] + nden[1] + nden[2]
net.symbols.variables       # frozenset({tgas})
net.symbols.tgas            # tgas