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#
# chemicalFormulas.py
#
# Copyright (c) 2003,2019 Paul McGuire
#
import pyparsing as pp
atomicWeight = {
"O": 15.9994,
"H": 1.00794,
"Na": 22.9897,
"Cl": 35.4527,
"C": 12.0107,
}
digits = "0123456789"
# Version 1
element = pp.Word(pp.alphas.upper(), pp.alphas.lower(), max=2).set_name("element")
# for stricter matching, use this Regex instead
# element = Regex("A[cglmrstu]|B[aehikr]?|C[adeflmorsu]?|D[bsy]|"
# "E[rsu]|F[emr]?|G[ade]|H[efgos]?|I[nr]?|Kr?|L[airu]|"
# "M[dgnot]|N[abdeiop]?|Os?|P[abdmortu]?|R[abefghnu]|"
# "S[bcegimnr]?|T[abcehilm]|U(u[bhopqst])?|V|W|Xe|Yb?|Z[nr]")
elementRef = pp.Group(element + pp.Opt(pp.Word(digits), default="1"))
formula = elementRef[...]
def sum_atomic_weights(element_list):
return sum(atomicWeight[elem] * int(qty) for elem, qty in element_list)
formula.runTests(
"""\
H2O
C6H5OH
NaCl
""",
fullDump=False,
postParse=lambda _, tokens: "Molecular weight: {}".format(
sum_atomic_weights(tokens)
),
)
print()
# Version 2 - access parsed items by results name
elementRef = pp.Group(
element("symbol") + pp.Opt(pp.Word(digits), default="1")("qty")
)
formula = elementRef[...]
def sum_atomic_weights_by_results_name(element_list):
return sum(atomicWeight[elem.symbol] * int(elem.qty) for elem in element_list)
formula.runTests(
"""\
H2O
C6H5OH
NaCl
""",
fullDump=False,
postParse=lambda _, tokens: "Molecular weight: {}".format(
sum_atomic_weights_by_results_name(tokens)
),
)
print()
# Version 3 - convert integers during parsing process
integer = pp.Word(digits).add_parse_action(lambda t: int(t[0])).set_name("integer")
elementRef = pp.Group(element("symbol") + pp.Opt(integer, default=1)("qty"))
formula = elementRef[...].set_name("chemical_formula")
def sum_atomic_weights_by_results_name_with_converted_ints(element_list):
return sum(atomicWeight[elem.symbol] * int(elem.qty) for elem in element_list)
formula.runTests(
"""\
H2O
C6H5OH
NaCl
""",
fullDump=False,
postParse=lambda _, tokens: "Molecular weight: {}".format(
sum_atomic_weights_by_results_name_with_converted_ints(tokens)
),
)
print()
# Version 4 - parse and convert integers as subscript digits
subscript_digits = "₀₁₂₃₄₅₆₇₈₉"
subscript_int_map = {e[1]: e[0] for e in enumerate(subscript_digits)}
def cvt_subscript_int(s):
ret = 0
for c in s[0]:
ret = ret * 10 + subscript_int_map[c]
return ret
subscript_int = pp.Word(subscript_digits).add_parse_action(cvt_subscript_int).set_name("subscript")
elementRef = pp.Group(element("symbol") + pp.Opt(subscript_int, default=1)("qty"))
formula = elementRef[1, ...].set_name("chemical_formula")
formula.runTests(
"""\
H₂O
C₆H₅OH
NaCl
""",
fullDump=False,
postParse=lambda _, tokens: "Molecular weight: {}".format(
sum_atomic_weights_by_results_name_with_converted_ints(tokens)
),
)
print()
|
