Printing a Tree data structure in Python

printing, python, python-2.7, tree

Solution

Yes, move the `__repr__` code to `__str__`, then call `str()` on your tree or pass it to the `print` statement. Remember to use `__str__` in the recursive calls too:

class node(object):
    def __init__(self, value, children = []):
        self.value = value
        self.children = children

    def __str__(self, level=0):
        ret = "\t"*level+repr(self.value)+"\n"
        for child in self.children:
            ret += child.__str__(level+1)
        return ret

    def __repr__(self):
        return '<tree node representation>'

Demo:

>>> root = node('grandmother')
>>> root.children = [node('daughter'), node('son')]
>>> root.children[0].children = [node('granddaughter'), node('grandson')]
>>> root.children[1].children = [node('granddaughter'), node('grandson')]
>>> root
<tree node representation>
>>> str(root)
"'grandmother'\n\t'daughter'\n\t\t'granddaughter'\n\t\t'grandson'\n\t'son'\n\t\t'granddaughter'\n\t\t'grandson'\n"
>>> print root
'grandmother'
    'daughter'
        'granddaughter'
        'grandson'
    'son'
        'granddaughter'
        'grandson'

Problem

I was looking for a possible implementation of tree printing, which prints the tree in a user-friendly way, and not as an instance of object. I came across this solution on the net: Source: http://cbio.ufs.ac.za/live_docs/nbn_tut/trees.html ``` class node(object): def __init__(self, value, children = []): self.value = value self.children = children def __repr__(self, level=0): ret = "\t"*level+repr(self.value)+"\n" for child in self.children: ret += child.__repr__(level+1) return ret ``` This code prints the tree in the following way: ``` 'grandmother' 'daughter' 'granddaughter' 'grandson' 'son' 'granddaughter' 'grandson' ``` Is it possible to have the same result but without changing the `__repr__` method, because I am using it for another purpose.

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