fork download
copy 
  1. import re
  2. from collections import defaultdict
  3.  
  4. _TOKENS = re.compile(r'(?:([A-Z][a-z]?)|\))(\d+)?|(\()')
  5.  
  6. def parse(formula):
  7.     counts = defaultdict(int)
  8.     stack = []
  9.     for token in _TOKENS.finditer(formula):
  10.         element, subscript, start_subformula = token.groups()
  11.         subscript = 1 if subscript is None else int(subscript)
  12.         if element:
  13.             counts[element] += 1 if subscript is None else subscript
  14.         elif start_subformula:
  15.             stack.append(counts)
  16.             counts = defaultdict(int)
  17.         else:
  18.             previous = stack.pop()
  19.             for elem, total in counts.items():
  20.                 previous[elem] += total * subscript
  21.             counts = previous
  22.     for element, total in sorted(counts.items()):
  23.         print '{:>2}: {}'.format(element, total)
  24.  
  25.  
  26. inputs = '''
  27. C6H12O6
  28. CCl2F2
  29. NaHCO3
  30. C4H8(OH)2
  31. PbCl(NH3)2(COOH)2'''
  32.  
  33. for line in inputs.splitlines():
  34.     print line
  35.     parse(line)
  36.     print
Success #stdin #stdout 0s 23688KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 

C6H12O6
 C: 6
 H: 12
 O: 6

CCl2F2
 C: 1
Cl: 2
 F: 2

NaHCO3
 C: 1
 H: 1
Na: 1
 O: 3

C4H8(OH)2
 C: 4
 H: 10
 O: 2

PbCl(NH3)2(COOH)2
 C: 2
Cl: 1
 H: 8
 N: 2
 O: 4
Pb: 1
https://ideone.com/HQZkW4
language:
Python (cpython 2.7.16)
created:
7 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!