How to convert version 3.x "yield from" to something compatible in version 2.7?

Question

This works fine with Python 3.5 .I understand yield from is not available in python 2.7. How can I implement the depth_first() function using python 2.7?

The following solution did not help me: Converting "yield from" statement to Python 2.7 code

class Node:
 def __init__(self, value):
    self._value = value
    self._children = []

 def __repr__(self):
    return 'Node({!r})'.format(self._value)

 def add_child(self, node):
    self._children.append(node)

 def __iter__(self):
    return iter(self._children)

 def depth_first(self):
    yield self
    for c in self:
        yield from c.depth_first()

# Example
if __name__ == '__main__':
    root = Node(0)
    child1 = Node(1)
    child2 = Node(2)
    root.add_child(child1)
    root.add_child(child2)
    child1.add_child(Node(3))
    child1.add_child(Node(4))
    child2.add_child(Node(5))
    for ch in root.depth_first():
        print(ch)

This is the expected output:

Node(0), Node(1), Node(3), Node(4), Node(2), Node(5)

@Prune Please look at my question, I specifically gave the link suggesting the solution did not work. Hope you read the question completely — Joe_12345, Aug 15 '17 at 00:17
What did you try that didn't work? What error did you get? (It worked for me.) — univerio, Aug 15 '17 at 00:39

score 1 · Accepted Answer · answered Aug 15 '17 at 00:40

Convert yield from into a for-loop with plain yield.

Convert class Node: into class Node(object): to ensure you get a new-style class.

The code now works in Python 2.7.

class Node(object):
 def __init__(self, value):
    self._value = value
    self._children = []

 def __repr__(self):
    return 'Node({!r})'.format(self._value)

 def add_child(self, node):
    self._children.append(node)

 def __iter__(self):
    return iter(self._children)

 def depth_first(self):
    yield self
    for c in self:
        for n in c.depth_first():
            yield n

# Example
if __name__ == '__main__':
    root = Node(0)
    child1 = Node(1)
    child2 = Node(2)
    root.add_child(child1)
    root.add_child(child2)
    child1.add_child(Node(3))
    child1.add_child(Node(4))
    child2.add_child(Node(5))
    for ch in root.depth_first():
        print(ch)

Note: this only works for trivial uses of `yield from`. If the caller is using `g.send` or other generator-specific functions, it does not. — o11c, Aug 15 '17 at 00:46

How to convert version 3.x "yield from" to something compatible in version 2.7?

1 Answers1