Dicionario
Publicado por Sara (1 intervención) el 08/11/2021 01:21:29
Steps
Do the following:
Change the compound list that is created in your make_periodic_table function to a dictionary. Each item in the dictionary should have a chemical symbol as the key and the chemical name and atomic mass in a list as the value, like this:
table = {
# symbol: [name, atomic_mass]
"Ac": ["Actinium", 227],
"Ag": ["Silver", 107.8682],
"Al": ["Aluminum", 26.9815386],
⋮
}
Copy and paste the following Python code into your chemistry.py program. Be certain not to paste the code inside an existing function.
class FormulaError(ValueError):
"""FormulaError is the type of error that
parse_formula will raise if a formula is invalid.
"""
pass
def parse_formula(formula, periodic_table_dict):
"""Convert a chemical formula for a molecule into a compound list
that stores the quantity of atoms of each element in the molecule.
For example, this function will convert "H2O" to [["H", 2], ["O", 1]]
and "PO4H2(CH2)12CH3" to [["P", 1], ["O", 4], ["H", 29], ["C", 13]]
"""
def parse_quant(formula, index):
quant = 1
if index < len(formula) and formula[index].isdecimal():
start = index
index += 1
while index < len(formula) and formula[index].isdecimal():
index += 1
quant = int(formula[start:index])
return quant, index
def get_quant(elems, symbol):
return 0 if symbol not in elems else elems[symbol]
def parse_r(formula, index, level):
start_index = index
start_level = level
elem_dict = {}
while index < len(formula):
ch = formula[index]
if ch == "(":
group_dict, index = parse_r(formula, index+1, level+1)
quant, index = parse_quant(formula, index)
for symbol in group_dict:
prev = get_quant(elem_dict, symbol)
elem_dict[symbol] = prev + group_dict[symbol] * quant
elif ch.isalpha():
symbol = formula[index:index+2]
if symbol in periodic_table_dict:
index += 2
else:
symbol = formula[index:index+1]
if symbol in periodic_table_dict:
index += 1
else:
raise FormulaError(
"invalid formula, unknown element symbol:",
formula, index)
quant, index = parse_quant(formula, index)
prev = get_quant(elem_dict, symbol)
elem_dict[symbol] = prev + quant
elif ch == ")":
if level == 0:
raise FormulaError(
"invalid formula, unmatched close parenthesis:",
formula, index)
level -= 1
index += 1
break
else:
if ch.isdecimal():
# Decimal digit not preceded by an
# element symbol or close parenthesis
message = "invalid formula:"
else:
# Illegal character: [^()0-9a-zA-Z]
message = "invalid formula, illegal character:"
raise FormulaError(message, formula, index)
if level > 0 and level >= start_level:
raise FormulaError(
"invalid formula, unmatched open parenthesis:",
formula, start_index - 1)
return elem_dict, index
# Return the compound list of element symbols and
# quantities. Each element in the compound list
# will be a list in this form: ["symbol", quantity]
elem_dict, _ = parse_r(formula, 0, 0)
return list(elem_dict.items())
# These are the indexes of the
# elements in the periodic table.
NAME_INDEX = 0
ATOMIC_MASS_INDEX = 1
def compute_molar_mass(symbol_quantity_list, periodic_table_dict):
"""Compute and return the total molar mass of all the
elements listed in symbol_quantity_list. Each element in
symbol_quantity_list is a list in the form: ["symbol", quantity].
As an example, if symbol_quantity_list is [["H", 2], ["O", 1]],
this function will calculate and return
atomic_mass("H") * 2 + atomic_mass("O") * 1
1.00794 * 2 + 15.9994 * 1
18.01528
"""
# For each element in the symbol_quantity_list:
# Split the element into symbol and quantity.
# Get the atomic mass for the symbol.
# Multiply the atomic mass by the quantity.
# Add the product into the total mass.
pass
The code that you pasted includes a function named parse_formula that converts a chemical formula for a molecule, such as "C13H16N2O2" (melatonin), into a compound list, such as [["C", 13], ["H", 16], ["N", 2], ["O", 2]]. In the code that you pasted, this compound list is known as a symbol_quantity_list because it contains the symbols of chemical elements and the quantity of each element that appears in the chemical formula.
The code that you pasted also includes the header and documentation string for a function named compute_molar_mass. Read the docstring and comments in the compute_molar_mass function and write the code for that function. Note that you can complete the compute_molar_mass function by writing eight or fewer lines of code.
Modify the main function in your chemistry.py program so that it does the following:
def main():
# Get a chemical formula for a molecule from the user.
# Get a mass in grams from the user.
# Call the make_periodic_table function and
# store the periodic table in a variable.
# Call the parse_formula function to convert the
# chemical formula given by the user to a compound
# list that stores element symbols and the quantity
# of atoms of each element in the molecule.
# Call the compute_molar_mass function to compute the
# molar mass of the molecule from the compound list.
# Compute the number of moles of the sample.
# Print the molar mass.
# Print the number of moles.
documento
def main():
formula = input("Enter the molecular formula of the sample:")
mass = input("Enter the mass in grams of the sample:")
periodic_table_dict = make_periodic_table()
symbol_quantity_list = [parse_formula (formula, periodic_table_dict)]
molar_mass = compute_molar_mass(symbol_quantity_list, periodic_table_dict)
print(f"{molar_mass} grams/mole")
print(f"{mass/molar_mass} moles")
def make_periodic_table():
table = {
# symbol [name, atomic_mass]
"Ac": ["Actinium", 227],
"Ag": ["Silver", 107.8682],
"Al": ["Aluminum", 26.9815386],
"Am": ["Americium", 243],
"Ar": ["Argon", 39.948],
"As": ["Arsenic", 74.9216],
"At": ["Astatine", 210],
"Au": ["Gold", 196.966569],
"B": ["Boron", 10.811],
"Ba": ["Barium", 137.327],
"Be": ["Beryllium", 9.012182],
"Bh": ["Bohrium", 272],
"Bi": ["Bismuth", 208.9804],
"Bk": ["Berkelium", 247],
"Br": ["Bromine", 79.904],
"C": ["Carbon", 12.0107],
"Ca": ["Calcium", 40.078],
"Cd": ["Cadmium", 112.411],
"Ce": ["Cerium", 140.116],
"Cf": ["Californium", 251],
"Cl": ["Chlorine", 35.453],
"Cm": ["Curium", 247],
"Cn": ["Copernicium", 285],
"Co": ["Cobalt", 58.933195],
"Cr": ["Chromium", 51.9961],
"Cs": ["Cesium", 132.9054519],
"Cu": ["Copper", 63.546],
"Db": ["Dubnium", 268],
"Ds": ["Darmstadtium", 281],
"Dy": ["Dysprosium", 162.5],
"Er": ["Erbium", 167.259],
"Es": ["Einsteinium", 252],
"Eu": ["Europium", 151.964],
"F": ["Fluorine", 18.9984032],
"Fe": ["Iron", 55.845],
"Fl": ["Flerovium", 289],
"Fm": ["Fermium", 257],
"Fr": ["Francium", 223],
"Ga": ["Gallium", 69.723],
"Gd": ["Gadolinium", 157.25],
"Ge": ["Germanium", 72.64],
"H": ["Hydrogen", 1.00794],
"He": ["Helium", 4.002602],
"Hf": ["Hafnium", 178.49],
"Hg": ["Mercury", 200.59],
"Ho": ["Holmium", 164.93032],
"Hs": ["Hassium", 270],
"I": ["Iodine", 126.90447],
"In": ["Indium", 114.818],
"Ir": ["Iridium", 192.217],
"K": ["Potassium", 39.0983],
"Kr": ["Krypton", 83.798],
"La": ["Lanthanum", 138.90547],
"Li": ["Lithium", 6.941],
"Lr": ["Lawrencium", 262],
"Lu": ["Lutetium", 174.9668],
"Lv": ["Livermorium", 293],
"Mc": ["Moscovium", 288],
"Md": ["Mendelevium", 258],
"Mg": ["Magnesium", 24.305],
"Mn": ["Manganese", 54.938045],
"Mo": ["Molybdenum", 95.96],
"Mt": ["Meitnerium", 276],
"N": ["Nitrogen", 14.0067],
"Na": ["Sodium", 22.98976928],
"Nb": ["Niobium", 92.90638],
"Nd": ["Neodymium", 144.242],
"Ne": ["Neon", 20.1797],
"Nh": ["Nihonium", 284],
"Ni": ["Nickel", 58.6934],
"No": ["Nobelium", 259],
"Np": ["Neptunium", 237],
"O": ["Oxygen", 15.9994],
"Og": ["Oganesson", 294],
"Os": ["Osmium", 190.23],
"P": ["Phosphorus", 30.973762],
"Pa": ["Protactinium", 231.03588],
"Pb": ["Lead", 207.2],
"Pd": ["Palladium", 106.42],
"Pm": ["Promethium", 145],
"Po": ["Polonium", 209],
"Pr": ["Praseodymium", 140.90765],
"Pt": ["Platinum", 195.084],
"Pu": ["Plutonium", 244],
"Ra": ["Radium", 226],
"Rb": ["Rubidium", 85.4678],
"Re": ["Rhenium", 186.207],
"Rf": ["Rutherfordium", 267],
"Rg": ["Roentgenium", 280],
"Rh": ["Rhodium", 102.9055],
"Rn": ["Radon", 222],
"Ru": ["Ruthenium", 101.07],
"S": ["Sulfur", 32.065],
"Sb": ["Antimony", 121.76],
"Sc": ["Scandium", 44.955912],
"Se": ["Selenium", 78.96],
"Sg": ["Seaborgium", 271],
"Si": ["Silicon", 28.0855],
"Sm": ["Samarium", 150.36],
"Sn": ["Tin", 118.71],
"Sr": ["Strontium", 87.62],
"Ta": ["Tantalum", 180.94788],
"Tb": ["Terbium", 158.92535],
"Tc": ["Technetium", 98],
"Te": ["Tellurium", 127.6],
"Th": ["Thorium", 232.03806],
"Ti": ["Titanium", 47.867],
"Tl": ["Thallium", 204.3833],
"Tm": ["Thulium", 168.93421],
"Ts": ["Tennessine", 294],
"U": ["Uranium", 238.02891],
"V": ["Vanadium", 50.9415],
"W": ["Tungsten", 183.84],
"Xe": ["Xenon", 131.293],
"Y": ["Yttrium", 88.90585],
"Yb": ["Ytterbium", 173.054],
"Zn": ["Zinc", 65.38],
"Zr": ["Zirconium", 91.224]
}
class FormulaError(ValueError):
"""FormulaError is the type of error that
parse_formula will raise if a formula is invalid.
"""
pass
def parse_formula(formula, periodic_table_dict):
"""Convert a chemical formula for a molecule into a compound list
that stores the quantity of atoms of each element in the molecule.
For example, this function will convert "H2O" to [["H", 2], ["O", 1]]
and "PO4H2(CH2)12CH3" to [["P", 1], ["O", 4], ["H", 29], ["C", 13]]
"""
def parse_quant(formula, index):
quant = 1
if index < len(formula) and formula[index].isdecimal():
start = index
index += 1
while index < len(formula) and formula[index].isdecimal():
index += 1
quant = int(formula[start:index])
return quant, index
def get_quant(elems, symbol):
return 0 if symbol not in elems else elems[symbol]
def parse_r(formula, index, level):
start_index = index
start_level = level
elem_dict = {}
while index < len(formula):
ch = formula[index]
if ch == "(":
group_dict, index = parse_r(formula, index+1, level+1)
quant, index = parse_quant(formula, index)
for symbol in group_dict:
prev = get_quant(elem_dict, symbol)
elem_dict[symbol] = prev + group_dict[symbol] * quant
elif ch.isalpha():
symbol = formula[index:index+2]
if symbol in periodic_table_dict:
index += 2
else:
symbol = formula[index:index+1]
if symbol in periodic_table_dict:
index += 1
else:
raise FormulaError(
"invalid formula, unknown element symbol:",
formula, index)
quant, index = parse_quant(formula, index)
prev = get_quant(elem_dict, symbol)
elem_dict[symbol] = prev + quant
elif ch == ")":
if level == 0:
raise FormulaError(
"invalid formula, unmatched close parenthesis:",
formula, index)
level -= 1
index += 1
break
else:
if ch.isdecimal():
# Decimal digit not preceded by an
# element symbol or close parenthesis
message = "invalid formula:"
else:
# Illegal character: [^()0-9a-zA-Z]
message = "invalid formula, illegal character:"
raise FormulaError(message, formula, index)
if level > 0 and level >= start_level:
raise FormulaError(
"invalid formula, unmatched open parenthesis:",
formula, start_index - 1)
return elem_dict, index
# Return the compound list of element symbols and
# quantities. Each element in the compound list
# will be a list in this form: ["symbol", quantity]
elem_dict, _ = parse_r(formula, 0, 0)
return list(elem_dict.items())
# These are the indexes of the
# elements in the periodic table.
NAME_INDEX = 0
ATOMIC_MASS_INDEX = 1
def compute_molar_mass(symbol_quantity_list, periodic_table_dict):
"""Compute and return the total molar mass of all the
elements listed in symbol_quantity_list. Each element in
symbol_quantity_list is a list in the form: ["symbol", quantity].
As an example, if symbol_quantity_list is [["H", 2], ["O", 1]],
this function will calculate and return
atomic_mass("H") * 2 + atomic_mass("O") * 1
1.00794 * 2 + 15.9994 * 1
18.01528
"""
# For each element in the symbol_quantity_list:
# Split the element into symbol and quantity.
# Get the atomic mass for the symbol.
# Multiply the atomic mass by the quantity.
# Add the product into the total mass.
for symbol, quantity in symbol_quantity_list:
atomic_mass = periodic_table_dict[symbol][ATOMIC_MASS_INDEX]
total_mass = atomic_mass * quantity
symbol_quantity_list.append(total_mass)
return total_mass
if __name__ == "__main__":
main()
Do the following:
Change the compound list that is created in your make_periodic_table function to a dictionary. Each item in the dictionary should have a chemical symbol as the key and the chemical name and atomic mass in a list as the value, like this:
table = {
# symbol: [name, atomic_mass]
"Ac": ["Actinium", 227],
"Ag": ["Silver", 107.8682],
"Al": ["Aluminum", 26.9815386],
⋮
}
Copy and paste the following Python code into your chemistry.py program. Be certain not to paste the code inside an existing function.
class FormulaError(ValueError):
"""FormulaError is the type of error that
parse_formula will raise if a formula is invalid.
"""
pass
def parse_formula(formula, periodic_table_dict):
"""Convert a chemical formula for a molecule into a compound list
that stores the quantity of atoms of each element in the molecule.
For example, this function will convert "H2O" to [["H", 2], ["O", 1]]
and "PO4H2(CH2)12CH3" to [["P", 1], ["O", 4], ["H", 29], ["C", 13]]
"""
def parse_quant(formula, index):
quant = 1
if index < len(formula) and formula[index].isdecimal():
start = index
index += 1
while index < len(formula) and formula[index].isdecimal():
index += 1
quant = int(formula[start:index])
return quant, index
def get_quant(elems, symbol):
return 0 if symbol not in elems else elems[symbol]
def parse_r(formula, index, level):
start_index = index
start_level = level
elem_dict = {}
while index < len(formula):
ch = formula[index]
if ch == "(":
group_dict, index = parse_r(formula, index+1, level+1)
quant, index = parse_quant(formula, index)
for symbol in group_dict:
prev = get_quant(elem_dict, symbol)
elem_dict[symbol] = prev + group_dict[symbol] * quant
elif ch.isalpha():
symbol = formula[index:index+2]
if symbol in periodic_table_dict:
index += 2
else:
symbol = formula[index:index+1]
if symbol in periodic_table_dict:
index += 1
else:
raise FormulaError(
"invalid formula, unknown element symbol:",
formula, index)
quant, index = parse_quant(formula, index)
prev = get_quant(elem_dict, symbol)
elem_dict[symbol] = prev + quant
elif ch == ")":
if level == 0:
raise FormulaError(
"invalid formula, unmatched close parenthesis:",
formula, index)
level -= 1
index += 1
break
else:
if ch.isdecimal():
# Decimal digit not preceded by an
# element symbol or close parenthesis
message = "invalid formula:"
else:
# Illegal character: [^()0-9a-zA-Z]
message = "invalid formula, illegal character:"
raise FormulaError(message, formula, index)
if level > 0 and level >= start_level:
raise FormulaError(
"invalid formula, unmatched open parenthesis:",
formula, start_index - 1)
return elem_dict, index
# Return the compound list of element symbols and
# quantities. Each element in the compound list
# will be a list in this form: ["symbol", quantity]
elem_dict, _ = parse_r(formula, 0, 0)
return list(elem_dict.items())
# These are the indexes of the
# elements in the periodic table.
NAME_INDEX = 0
ATOMIC_MASS_INDEX = 1
def compute_molar_mass(symbol_quantity_list, periodic_table_dict):
"""Compute and return the total molar mass of all the
elements listed in symbol_quantity_list. Each element in
symbol_quantity_list is a list in the form: ["symbol", quantity].
As an example, if symbol_quantity_list is [["H", 2], ["O", 1]],
this function will calculate and return
atomic_mass("H") * 2 + atomic_mass("O") * 1
1.00794 * 2 + 15.9994 * 1
18.01528
"""
# For each element in the symbol_quantity_list:
# Split the element into symbol and quantity.
# Get the atomic mass for the symbol.
# Multiply the atomic mass by the quantity.
# Add the product into the total mass.
pass
The code that you pasted includes a function named parse_formula that converts a chemical formula for a molecule, such as "C13H16N2O2" (melatonin), into a compound list, such as [["C", 13], ["H", 16], ["N", 2], ["O", 2]]. In the code that you pasted, this compound list is known as a symbol_quantity_list because it contains the symbols of chemical elements and the quantity of each element that appears in the chemical formula.
The code that you pasted also includes the header and documentation string for a function named compute_molar_mass. Read the docstring and comments in the compute_molar_mass function and write the code for that function. Note that you can complete the compute_molar_mass function by writing eight or fewer lines of code.
Modify the main function in your chemistry.py program so that it does the following:
def main():
# Get a chemical formula for a molecule from the user.
# Get a mass in grams from the user.
# Call the make_periodic_table function and
# store the periodic table in a variable.
# Call the parse_formula function to convert the
# chemical formula given by the user to a compound
# list that stores element symbols and the quantity
# of atoms of each element in the molecule.
# Call the compute_molar_mass function to compute the
# molar mass of the molecule from the compound list.
# Compute the number of moles of the sample.
# Print the molar mass.
# Print the number of moles.
documento
def main():
formula = input("Enter the molecular formula of the sample:")
mass = input("Enter the mass in grams of the sample:")
periodic_table_dict = make_periodic_table()
symbol_quantity_list = [parse_formula (formula, periodic_table_dict)]
molar_mass = compute_molar_mass(symbol_quantity_list, periodic_table_dict)
print(f"{molar_mass} grams/mole")
print(f"{mass/molar_mass} moles")
def make_periodic_table():
table = {
# symbol [name, atomic_mass]
"Ac": ["Actinium", 227],
"Ag": ["Silver", 107.8682],
"Al": ["Aluminum", 26.9815386],
"Am": ["Americium", 243],
"Ar": ["Argon", 39.948],
"As": ["Arsenic", 74.9216],
"At": ["Astatine", 210],
"Au": ["Gold", 196.966569],
"B": ["Boron", 10.811],
"Ba": ["Barium", 137.327],
"Be": ["Beryllium", 9.012182],
"Bh": ["Bohrium", 272],
"Bi": ["Bismuth", 208.9804],
"Bk": ["Berkelium", 247],
"Br": ["Bromine", 79.904],
"C": ["Carbon", 12.0107],
"Ca": ["Calcium", 40.078],
"Cd": ["Cadmium", 112.411],
"Ce": ["Cerium", 140.116],
"Cf": ["Californium", 251],
"Cl": ["Chlorine", 35.453],
"Cm": ["Curium", 247],
"Cn": ["Copernicium", 285],
"Co": ["Cobalt", 58.933195],
"Cr": ["Chromium", 51.9961],
"Cs": ["Cesium", 132.9054519],
"Cu": ["Copper", 63.546],
"Db": ["Dubnium", 268],
"Ds": ["Darmstadtium", 281],
"Dy": ["Dysprosium", 162.5],
"Er": ["Erbium", 167.259],
"Es": ["Einsteinium", 252],
"Eu": ["Europium", 151.964],
"F": ["Fluorine", 18.9984032],
"Fe": ["Iron", 55.845],
"Fl": ["Flerovium", 289],
"Fm": ["Fermium", 257],
"Fr": ["Francium", 223],
"Ga": ["Gallium", 69.723],
"Gd": ["Gadolinium", 157.25],
"Ge": ["Germanium", 72.64],
"H": ["Hydrogen", 1.00794],
"He": ["Helium", 4.002602],
"Hf": ["Hafnium", 178.49],
"Hg": ["Mercury", 200.59],
"Ho": ["Holmium", 164.93032],
"Hs": ["Hassium", 270],
"I": ["Iodine", 126.90447],
"In": ["Indium", 114.818],
"Ir": ["Iridium", 192.217],
"K": ["Potassium", 39.0983],
"Kr": ["Krypton", 83.798],
"La": ["Lanthanum", 138.90547],
"Li": ["Lithium", 6.941],
"Lr": ["Lawrencium", 262],
"Lu": ["Lutetium", 174.9668],
"Lv": ["Livermorium", 293],
"Mc": ["Moscovium", 288],
"Md": ["Mendelevium", 258],
"Mg": ["Magnesium", 24.305],
"Mn": ["Manganese", 54.938045],
"Mo": ["Molybdenum", 95.96],
"Mt": ["Meitnerium", 276],
"N": ["Nitrogen", 14.0067],
"Na": ["Sodium", 22.98976928],
"Nb": ["Niobium", 92.90638],
"Nd": ["Neodymium", 144.242],
"Ne": ["Neon", 20.1797],
"Nh": ["Nihonium", 284],
"Ni": ["Nickel", 58.6934],
"No": ["Nobelium", 259],
"Np": ["Neptunium", 237],
"O": ["Oxygen", 15.9994],
"Og": ["Oganesson", 294],
"Os": ["Osmium", 190.23],
"P": ["Phosphorus", 30.973762],
"Pa": ["Protactinium", 231.03588],
"Pb": ["Lead", 207.2],
"Pd": ["Palladium", 106.42],
"Pm": ["Promethium", 145],
"Po": ["Polonium", 209],
"Pr": ["Praseodymium", 140.90765],
"Pt": ["Platinum", 195.084],
"Pu": ["Plutonium", 244],
"Ra": ["Radium", 226],
"Rb": ["Rubidium", 85.4678],
"Re": ["Rhenium", 186.207],
"Rf": ["Rutherfordium", 267],
"Rg": ["Roentgenium", 280],
"Rh": ["Rhodium", 102.9055],
"Rn": ["Radon", 222],
"Ru": ["Ruthenium", 101.07],
"S": ["Sulfur", 32.065],
"Sb": ["Antimony", 121.76],
"Sc": ["Scandium", 44.955912],
"Se": ["Selenium", 78.96],
"Sg": ["Seaborgium", 271],
"Si": ["Silicon", 28.0855],
"Sm": ["Samarium", 150.36],
"Sn": ["Tin", 118.71],
"Sr": ["Strontium", 87.62],
"Ta": ["Tantalum", 180.94788],
"Tb": ["Terbium", 158.92535],
"Tc": ["Technetium", 98],
"Te": ["Tellurium", 127.6],
"Th": ["Thorium", 232.03806],
"Ti": ["Titanium", 47.867],
"Tl": ["Thallium", 204.3833],
"Tm": ["Thulium", 168.93421],
"Ts": ["Tennessine", 294],
"U": ["Uranium", 238.02891],
"V": ["Vanadium", 50.9415],
"W": ["Tungsten", 183.84],
"Xe": ["Xenon", 131.293],
"Y": ["Yttrium", 88.90585],
"Yb": ["Ytterbium", 173.054],
"Zn": ["Zinc", 65.38],
"Zr": ["Zirconium", 91.224]
}
class FormulaError(ValueError):
"""FormulaError is the type of error that
parse_formula will raise if a formula is invalid.
"""
pass
def parse_formula(formula, periodic_table_dict):
"""Convert a chemical formula for a molecule into a compound list
that stores the quantity of atoms of each element in the molecule.
For example, this function will convert "H2O" to [["H", 2], ["O", 1]]
and "PO4H2(CH2)12CH3" to [["P", 1], ["O", 4], ["H", 29], ["C", 13]]
"""
def parse_quant(formula, index):
quant = 1
if index < len(formula) and formula[index].isdecimal():
start = index
index += 1
while index < len(formula) and formula[index].isdecimal():
index += 1
quant = int(formula[start:index])
return quant, index
def get_quant(elems, symbol):
return 0 if symbol not in elems else elems[symbol]
def parse_r(formula, index, level):
start_index = index
start_level = level
elem_dict = {}
while index < len(formula):
ch = formula[index]
if ch == "(":
group_dict, index = parse_r(formula, index+1, level+1)
quant, index = parse_quant(formula, index)
for symbol in group_dict:
prev = get_quant(elem_dict, symbol)
elem_dict[symbol] = prev + group_dict[symbol] * quant
elif ch.isalpha():
symbol = formula[index:index+2]
if symbol in periodic_table_dict:
index += 2
else:
symbol = formula[index:index+1]
if symbol in periodic_table_dict:
index += 1
else:
raise FormulaError(
"invalid formula, unknown element symbol:",
formula, index)
quant, index = parse_quant(formula, index)
prev = get_quant(elem_dict, symbol)
elem_dict[symbol] = prev + quant
elif ch == ")":
if level == 0:
raise FormulaError(
"invalid formula, unmatched close parenthesis:",
formula, index)
level -= 1
index += 1
break
else:
if ch.isdecimal():
# Decimal digit not preceded by an
# element symbol or close parenthesis
message = "invalid formula:"
else:
# Illegal character: [^()0-9a-zA-Z]
message = "invalid formula, illegal character:"
raise FormulaError(message, formula, index)
if level > 0 and level >= start_level:
raise FormulaError(
"invalid formula, unmatched open parenthesis:",
formula, start_index - 1)
return elem_dict, index
# Return the compound list of element symbols and
# quantities. Each element in the compound list
# will be a list in this form: ["symbol", quantity]
elem_dict, _ = parse_r(formula, 0, 0)
return list(elem_dict.items())
# These are the indexes of the
# elements in the periodic table.
NAME_INDEX = 0
ATOMIC_MASS_INDEX = 1
def compute_molar_mass(symbol_quantity_list, periodic_table_dict):
"""Compute and return the total molar mass of all the
elements listed in symbol_quantity_list. Each element in
symbol_quantity_list is a list in the form: ["symbol", quantity].
As an example, if symbol_quantity_list is [["H", 2], ["O", 1]],
this function will calculate and return
atomic_mass("H") * 2 + atomic_mass("O") * 1
1.00794 * 2 + 15.9994 * 1
18.01528
"""
# For each element in the symbol_quantity_list:
# Split the element into symbol and quantity.
# Get the atomic mass for the symbol.
# Multiply the atomic mass by the quantity.
# Add the product into the total mass.
for symbol, quantity in symbol_quantity_list:
atomic_mass = periodic_table_dict[symbol][ATOMIC_MASS_INDEX]
total_mass = atomic_mass * quantity
symbol_quantity_list.append(total_mass)
return total_mass
if __name__ == "__main__":
main()
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