tree4streams.py, 'p4 streams' as tree - Calls 'p4 streams', parses the output, and prints all streams as a tree.

tree4streams.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import shlex
import StringIO
import subprocess

class P4Stream:
    def __init__(self, parent_name=None):
        self.parent_name = parent_name
        self.children_names = set() # will be initialized when the whole tree is known

class P4StreamTree:
    def __init__(self):
        self.__streams = {} # all streams known
        self.__root_stream_names = set() # all streams without parent known
        self.__immutable = False

    def __str__(self):
        if not self.__immutable:
            raise RuntimeError('Tree shall be built first')
        result = ''
        for root_stream_name in sorted(self.__root_stream_names):
            result += self.__stream_and_its_children_to_string(root_stream_name)
        return result

    def add_stream(self, stream_name, parent_stream_name):
        if self.__immutable:
            raise RuntimeError('Tree is immutable')
        child_stream = P4Stream(parent_stream_name if parent_stream_name != 'none' else None)
        self.__streams[stream_name] = child_stream
        if parent_stream_name == 'none':
            self.__root_stream_names.add(stream_name)

    def build(self):
        """Initializes the links parent -> child. Afterwards, the tree will be immutable.
        """
        self.__immutable = True
        for child_stream_name, child_stream in self.__streams.iteritems():
            parent_stream_name = child_stream.parent_name
            if parent_stream_name is not None:
                self.__streams[parent_stream_name].children_names.add(child_stream_name)

    def __stream_and_its_children_to_string(self, stream_name, indentation=0):
        result = '%s%s\n' % (' ' * indentation, stream_name)
        indentation += 2
        for child_stream_name in sorted(self.__streams[stream_name].children_names):
            result += self.__stream_and_its_children_to_string(child_stream_name, indentation)
        return result

def _main():
    """Calls 'p4 stream', parses the output, and prints all streams as a tree.
    """
    p4_streams = subprocess.check_output(shlex.split('p4 streams'))
    tree = P4StreamTree()
    for line in StringIO.StringIO(p4_streams):
        # Such a line looks like
        # "Stream //my-depot/my-child-stream type //my-depot/my-parent-stream 'description'"
        info = line.split()
        tree.add_stream(info[1], info[3])
    tree.build()
    print(tree)

if __name__ == "__main__":
    _main()