thanks Aaron, Paul and Vlastimil,
sorry I phrased my question wrong,
I was looking for parsing an expression of an element of a nested list
the code below seems to do what I'm looking for.
cheers,
Stef
Aaron Brady wrote:
On Mar 15, 6:44 pm, Stef Mientki <stef.mien...@gmail.com> wrote:
hello,
I need to parse a nested list, given as a string, like this
line = " A [ B [ C+2 ] + 3 ] "
( I probably can do it with find, but I guess that's not the most
elegant way, besides recusrion is not my strongest point)
which should be parsed so I get an list from inner to outer side (don't
know if these are the correct words),
but I should like to have a list or tuple for tis case:
parsed = [ C+2, B[C+2]+3, A [ B [ C+2 ] + 3 ] ]
or (last term is not needed, as well as the constants aren't)
parsed = [ C, B[C+2] ]
this all, to improve the improved error / exception message even more ;-)
thanks,
Stef
Hi Stef,
This looks like what you want:
def parse_list( s, start= 0 ):
x= []
i= start
while i< len( s ):
c= s[ i ]
if c== '[':
y, i= parse_list( s, i+ 1 )
x= x+ y
if c== ']':
return x+ [ s[start: i ] ], i
i+= 1
return x+ [ s ]
line = " A [ B [ C+2 ] + 3 ] "
print( parse_list( line ) )
#[' C+2 ', ' B [ C+2 ] + 3 ', ' A [ B [ C+2 ] + 3 ] ']
line = " A [ B [ C+2 ] [ D+2 ] + 3 ] "
print( parse_list( line ) )
#[' C+2 ', ' D+2 ', ' B [ C+2 ] [ D+2 ] + 3 ', ' A [ B [ C+2 ] [ D
+2 ] + 3 ] ']
...So long as you don't have any brackets inside strings or what not.
It just admits two special characters, '[' and ']'.
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