pyparsing性能和内存使用

Question

Pyparsing运行良好的一个非常小的语法，但语法的不断壮大，性能下降，并通过屋顶的内存使用情况。

我现在gramar是：

newline = LineEnd() 
minus = Literal ('-') 
plus = Literal ('+') 
star = Literal ('*') 
dash = Literal ('/') 
dashdash = Literal ('//') 
percent = Literal ('%') 
starstar = Literal ('**') 
lparen = Literal ('(') 
rparen = Literal (')') 
dot = Literal ('.') 
comma = Literal (',') 
eq = Literal ('=') 
eqeq = Literal ('==') 
lt = Literal ('<') 
gt = Literal ('>') 
le = Literal ('<=') 
ge = Literal ('>=') 
not_ = Keyword ('not') 
and_ = Keyword ('and') 
or_ = Keyword ('or') 
ident = Word (alphas) 
integer = Word (nums) 

expr = Forward() 
parenthized = Group (lparen + expr + rparen) 
trailer = (dot + ident) 
atom = ident | integer | parenthized 
factor = Forward() 
power = atom + ZeroOrMore (trailer) + Optional (starstar + factor) 
factor << (ZeroOrMore (minus | plus) + power) 
term = ZeroOrMore (factor + (star | dashdash | dash | percent)) + factor 
arith = ZeroOrMore (term + (minus | plus)) + term 
comp = ZeroOrMore (arith + (eqeq | le | ge | lt | gt)) + arith 
boolNot = ZeroOrMore (not_) + comp 
boolAnd = ZeroOrMore (boolNot + and_) + boolNot 
boolOr = ZeroOrMore (boolAnd + or_) + boolAnd 
match = ZeroOrMore (ident + eq) + boolOr 
expr << match 
statement = expr + newline 
program = OneOrMore (statement) 

当我解析以下

print (program.parseString ('3*(1+2*3*(4+5))\n')) 

这需要相当长的：

~/Desktop/m2/pyp$ time python3 slow.py 
['3', '*', ['(', '1', '+', '2', '*', '3', '*', ['(', '4', '+', '5', ')'], ')']] 

real 0m27.280s 
user 0m25.844s 
sys 0m1.364s 

而且内存使用量上升到1.7吉布（原文如此！）。

有我做了一些严重的错误执行这一语法还是我还能如何保持内存使用情况在可以忍受的利润率？

Answer 1

进口pyparsing使packrat解析到memoize的解析行为后：

ParserElement.enablePackrat() 

这应该使性能有了很大的改进。