This is a general problem with pyparsing and python 2.7 (in 3 it works just fine). The general structure is this:
class SomeParser(object):
def some_action(self, string, loc, tok):
print("action")
def gramma(self):
...pyparsing gramma for some
language....
some_rule = (token + token2).setParseAction(self.some_action)
return some_rule
def parse(self, string):
self.gramma().parseString(string)
return True
In python3 pyparsing works just fine, in 2.7 however I get
Parsing error : some_action() takes exactly 4 arguments (1 given)
My question is how to make it work in both versions?
EDIT: After some test I found that it is general problem, not only with class methods.
I think I found a problem (with a help of a friend), which is in pyparsing 1.5.6 and its _trim_arity function that tries to guess the number of arguments that func in setParseAction(func) is accepting. I changed it from:
if not _PY3K:
def _trim_arity(func, maxargs=2):
limit = [0]
def wrapper(*args):
while 1:
try:
return func(*args[limit[0]:])
except TypeError:
if limit[0] <= maxargs:
limit[0] += 1
continue
raise
return wrapper
else:
def _trim_arity(func, maxargs=2):
limit = maxargs
def wrapper(*args):
#~ nonlocal limit
while 1:
try:
return func(*args[limit:])
except TypeError:
if limit:
limit -= 1
continue
raise
return wrapper
to:
if not _PY3K and False:
def _trim_arity(func, maxargs=2):
limit = [0]
def wrapper(*args):
while 1:
try:
return func(*args[limit[0]:])
except TypeError:
if limit[0] <= maxargs:
limit[0] += 1
continue
raise
return wrapper
else:
def _trim_arity(func, maxargs=2):
# limit = maxargs
def wrapper(*args):
limit = maxargs
#~ nonlocal limit
while 1:
try:
return func(*args[limit:])
except TypeError:
if limit:
limit -= 1
continue
raise
return wrapper
Not very elegant but I can see that in the trunk version on pyparsing it is fixed already.