Reputation: 1039
Let's suppose to have this sum of products boolean expresion in prefix form:
str_formula = 'Or(A, And(B, C, D), E, F, And(G, H))'
Or
and And
are the only operators permitted and there is no more nesting structure than the one representing above . I would like to rewrite the expression in order to receive the infix form.
My idea, without using regular expressions, was:
import ast
import re
or_op = ' OR '
and_op = ' AND '
str_formula = str_formula.replace('Or(', '[').replace('And(', '[').replace(')', ']')
s_list = re.sub('(\w+)', r"'\1'", str_formula)
list_formula = [x if isinstance(x, list) else [x] for x in ast.literal_eval(s_list)]
infix_form = or_op.join([and_op.join(sublist) for sublist in list_formula])
The infix_form variable is:
'A OR B AND C AND D OR E OR F OR G AND H'
Can you suggest a regex in order to solve in a smarter way this problem?
Upvotes: 2
Views: 499
Reputation: 92854
Consider the following approach using re.sub()
function with replacement callback replaceOperands
:
str_formula = 'Or(A, And(B, C, D), E, F, And(G, H))'
def replaceOperands(m):
s = re.sub(r'\(|\)', '', m.group(2).replace(',', ' OR')) if m.group(1) == 'Or' else '('+m.group(2).replace(',', ' AND')+')'
return s
str_formula = re.sub(r'\b(Or)\(([A-Z], (?:\(.*\))[A-Z]?)',
replaceOperands,
re.sub(r'\b(And)\(([^)]+)\)', replaceOperands, str_formula))
print(str_formula)
The output:
A OR B AND C AND D OR E OR F OR G AND H
Upvotes: 1