Question

So I wanted to make an arff reader (similar to csv file format).

And I wanted to use yield to make an iterator but also to add attributes to this iterator.

eg:

data = arff.reader(my_fname)
print data.relation
for row in data:
    print row

but in the reader definition:

def reader(fname):
    reader.relation = fname # this is assigned to the function, not the generator
    yield 1
    yield 2

Is there a way to do this using yield or am I stuck with the iterator api?

Answer 1

You can make it a class.

class Reader(object): # Assuming Python <= 2.7
    def __init__(self, fname):
        self.fname = fname

    def __iter__(self):
        yield 1
        yield 2

r = Reader("some file")
print r.fname ## 'some file'
for line in r:
    print line ## 1 then 2