Jeremy's thing

thing_finder.py

things = """
L 855.91
PhNHPz 158.072
tBuPhNHPz 214.135
pyDAPz 239.093
OAc 59.014
Fe 55.933
O 15.996
OH 17.003
H2O 18.011
Cl 34.969
OTf 148.952
"""

limits = """
L = 1
PhNHPz < 5
tBuPhNHPz < 5
pyDAPz < 5
Fe < 8
O < 3
OH < 3
H2O < 3
Cl < 5
"""

target_mass = 1736
threshold = 2 # The `abs(x-x') < precision` we need to sum our masses up to

# ----------------------------- #
# ----------------------------- #
# ----------------------------- #

# Lets parse the things first
new_things = {}
for line in things.split("\n"):
    line_split = line.split()
    if len(line_split) == 2:
        new_things[line_split[0]] = float(line_split[1])

def parse_limit(thing, op, num):
    num = int(num)

    if op == "<":
        def limit(soln):
            if thing in soln:
                return soln[thing] < num
            return True
        return limit
    elif op == ">":
        def limit(soln):
            if thing not in soln:
                return False
            return soln[thing] > num
        return limit
    elif op == "=":
        def limit(soln):
            if thing not in soln:
                return num == 0
            return soln[thing] == num
        return limit
    else:
        raise Exception("Unknown comparison `%s`!" % op)

new_limits = []
for line in limits.split("\n"):
    line_split = line.split()
    if len(line_split) == 3:
        limit = parse_limit(line_split[0], line_split[1], line_split[2])
        new_limits.append(limit)

limits = new_limits
things = new_things
keys = list(things.keys())

def search(solution, i, leftover_mass):
    global things
    global threshold
    global keys

    if i != len(things):
        solution = solution[:] # Clone the solution (sin)

        while leftover_mass > 0:
            if abs(leftover_mass) < threshold:
                break

            search(solution, i + 1, leftover_mass)
            solution[i] += 1
            leftover_mass -= things[keys[i]]

    if abs(leftover_mass) < threshold:

        # We gotta prepare a proper solution to print now
        soln = {}
        mass = 0
        for i in range(0, len(things)):
            if solution[i] == 0:
                continue
            mass += things[keys[i]] * solution[i]
            soln[keys[i]] = solution[i]

        for limit in limits:
            if not limit(soln):
                return

        print("Solution:", soln, "with mass", mass)

search([0] * len(things), 0, target_mass)