write a recognizer

[Klaus Neuner]

Hello,

I want to write a class Recognizer, like so:

class Recognizer(obje ct):

def is_of_category_ 1(self, token):
if token == 1:
return "1"
else:
return False

def is_of_category_ 2(self, token):
if token == 2:
return "2"
else:
return False

def recognize(self, token):
for fun in <?>:
result = apply(fun, token)
if result:
return result
return False

What do I have to write instead of <?>?
Or: How should I design the recognizer, if the above design is not good?

Klaus

[Peter Otten]

Klaus Neuner wrote:

Hello,

I want to write a class Recognizer, like so:

class Recognizer(obje ct):

def is_of_category_ 1(self, token):
if token == 1:
return "1"
else:
return False

def is_of_category_ 2(self, token):
if token == 2:
return "2"
else:
return False

def recognize(self, token):
for fun in <?>:
result = apply(fun, token)
if result:
return result
return False

What do I have to write instead of <?>?
Or: How should I design the recognizer, if the above design is not good?

Klaus

The following assumes that all category checker method names start with a
common prefix. Those are automatically extracted in the __init__() method.
If you are interested in this technique, I stole it from cmd.py in the
library. IIRC, the implementation is more complete as it also inspects the
base classes.

class Recognizer(obje ct):
def __init__(self):
r = self.recognizer s = []
for n in dir(self.__clas s__):
if n.startswith("i s_"):
r.append(getatt r(self, n))

def is_of_category_ 1(self, token):
if token == 1:
return "1"

def is_of_category_ 2(self, token):
if token == 2:
return "2"

def recognize(self, token):
# would also work:
#for fun in [self.is_of_cate gory_1, self.is_of_cate gory_2]:

for fun in self.recognizer s:
result = fun(token)
if result:
return result
return False

if __name__ == "__main__":
r = Recognizer()
for t in "12341":
print r.recognize(int (t)),
print

Peter

[Chunming Luo]

Peter Otten wrote:

Klaus Neuner wrote:

Hello,

I want to write a class Recognizer, like so:

class Recognizer(obje ct):

def is_of_category_ 1(self, token):
if token == 1:
return "1"
else:
return False

def is_of_category_ 2(self, token):
if token == 2:
return "2"
else:
return False

def recognize(self, token):
for fun in <?>:
result = apply(fun, token)
if result:
return result
return False

What do I have to write instead of <?>?
Or: How should I design the recognizer, if the above design is not good?

Klaus

The following assumes that all category checker method names start with a
common prefix. Those are automatically extracted in the __init__() method.
If you are interested in this technique, I stole it from cmd.py in the
library. IIRC, the implementation is more complete as it also inspects the
base classes.

class Recognizer(obje ct):
def __init__(self):
r = self.recognizer s = []
for n in dir(self.__clas s__):
if n.startswith("i s_"):
r.append(getatt r(self, n))

def is_of_category_ 1(self, token):
if token == 1:
return "1"

def is_of_category_ 2(self, token):
if token == 2:
return "2"

def recognize(self, token):
# would also work:
#for fun in [self.is_of_cate gory_1, self.is_of_cate gory_2]:

for fun in self.recognizer s:
result = fun(token)
if result:
return result
return False

if __name__ == "__main__":
r = Recognizer()
for t in "12341":
print r.recognize(int (t)),
print

Peter

Here is another solution:

def recongnize(self , token):
for item in self.__class__. __dict__.keys() :
method = self.__class__. __dict__[item]
if callable(method ) and method !=
self.__class__. __dict__["recongnize "]:
result = method(self, token)
if result:
return result
return false

-Chunming

[max khesin]

This is cool. Curious (my py object recall is a bit stale): would this
solution work for a class that derives from Recognizer (and implements
an 'is_' method)?

thanks,
max
Peter Otten wrote:

Klaus Neuner wrote:

Hello,

I want to write a class Recognizer, like so:

class Recognizer(obje ct):

def is_of_category_ 1(self, token):
if token == 1:
return "1"
else:
return False

def is_of_category_ 2(self, token):
if token == 2:
return "2"
else:
return False

def recognize(self, token):
for fun in <?>:
result = apply(fun, token)
if result:
return result
return False

What do I have to write instead of <?>?
Or: How should I design the recognizer, if the above design is not good?

Klaus

The following assumes that all category checker method names start with a
common prefix. Those are automatically extracted in the __init__() method.
If you are interested in this technique, I stole it from cmd.py in the
library. IIRC, the implementation is more complete as it also inspects the
base classes.

class Recognizer(obje ct):
def __init__(self):
r = self.recognizer s = []
for n in dir(self.__clas s__):
if n.startswith("i s_"):
r.append(getatt r(self, n))

def is_of_category_ 1(self, token):
if token == 1:
return "1"

def is_of_category_ 2(self, token):
if token == 2:
return "2"

def recognize(self, token):
# would also work:
#for fun in [self.is_of_cate gory_1, self.is_of_cate gory_2]:

for fun in self.recognizer s:
result = fun(token)
if result:
return result
return False

if __name__ == "__main__":
r = Recognizer()
for t in "12341":
print r.recognize(int (t)),
print

Peter

[Peter Otten]

max khesin wrote:

This is cool. Curious (my py object recall is a bit stale): would this
solution work for a class that derives from Recognizer (and implements
an 'is_' method)?

No, but you can use the following instead of dir(...) in the for loop of
__init__():

(copied from cmd.py in the libarary)

def get_names(self) :
# Inheritance says we have to look in class and
# base classes; order is not important.
names = []
classes = [self.__class__]
while classes:
aclass = classes.pop(0)
if aclass.__bases_ _:
classes = classes + list(aclass.__b ases__)
names = names + dir(aclass)
return names

Peter

[Klaus Neuner]

Thanks to all who participated in this thread.