How to make a custom object iterable?

Question

I have a list of custom-class objects (sample is below).

Using: list(itertools.chain.from_iterable(myBigList)) I wanted to \"merge\" all o

Answer 1

You can subclass list as well:

class Direction(list):
    def __init__(self, seq=[], id_=None):
        list.__init__(self,seq)
        self.id = id_ if id_ else id(self)

    def __iter__(self):
        it=list.__iter__(self) 
        next(it)                       # skip the first...
        return it  

d=Direction(range(10))
print(d)       # all the data, no iteration
# [0, 1, 2, 3, 4]

print (', '.join(str(e) for e in d))     # 'for e in d' is an iterator
# 1, 2, 3, 4

ie, skips the first.

Works for nested lists as well:

>>> d1=Direction([range(5), range(10,15), range(20,25)])
>>> d1
[range(0, 5), range(10, 15), range(20, 25)]
print(list(itertools.chain.from_iterable(d1)))
[10, 11, 12, 13, 14, 20, 21, 22, 23, 24]