from NIST.Isotopes import Query
from SciNum import DecimalWithUnits as DwU

q = Query()
n = DwU('8', 'mol')
for formula in ('CH4', 'O2', 'CO2', 'InChI=1S/C4H5As/c1-2-4-5-3-1/h1-5H'):
  mol_mass = q.molecular_weight(formula)
  print(formula, ':', mol_mass, '*', n, '=', mol_mass * n)

#!/usr/bin/env python3

"""
A very simple example of using SciNum and NIST.PhysicalConstants to calculate
the pressure of an ideal gas.

The following are demonstrated:

* retrieval of physical constants
* declaration of physical quantities
* basic arithmetic
* reduction to SI base units
* expression in desired units by substitution
"""

from SciNum import DecimalWithUnits as DwU, MeasuredDecimalWithUnits as MDwU
from SciNum.units import Units, Definition, SI_DERIVED_UNIT_DEFINITIONS
from SciNum.units import reduce_to_base_units, express
from NIST.PhysicalConstants import PhysicalConstants

pc = PhysicalConstants()

# This is just to show unit multiplication.
k_b = pc['Boltzmann constant']
N_A = pc['Avogadro constant']
R = k_b * N_A

# This would work as well
# R = pc['molar gas constant']

# Measured decimals are used here to keep track of significant figures. Each
# number has 3 and so 3 sigfigs will be included in the output. Digits beyond
# those are just placeholders.
n = MDwU('5.00', 'mol')
T = MDwU('300', 'K')
V = MDwU('2.00', 'm^3')

# Calculate the pressure p from the ideal gas law.
p = (n * R * T) / V

# Display some output.
print("Given:")
print('k_b =', k_b)
print('N_A =', N_A)
# Display fewer digits for R.
print('R =', format(R, '.5f'))
print('n =', n)
print('T =', T)
print('V =', V)
print()

print("Rearranging the ideal gas law (pV = nRT) to solve for p")
print("p = (nRT)/V")
print("p = (%s * %s * %s)/(%s)" % (n, format(R, '.5f'), T, V))
print("p = (%s)/(%s)" % (n * R * T, V))

# Express p in default units (whatever the constants and the above values happen
# to be expressed in).
print('p =', format(p, 'f'), "(%d significant figure(s))" % p.precision)

# Express p in SI base units.
p_SI = p.reduce_to_base_units()
print('  =', format(p_SI, 'f'))

# Express p in Pa
# The Definition for Pa could have been created directly instead of manipulating
# SI_DERIVED_UNIT_DEFINITIONS.
Pa_base, Pa_factor = reduce_to_base_units(SI_DERIVED_UNIT_DEFINITIONS['Pa'])
Pa_def = Definition('Pa', Pa_base, Pa_factor)
m_def = express(Pa_def, 'm')
p_Pa = p_SI.substitute_units((m_def,))
print('  =', format(p_Pa, 'f'))