Blueprint for dumper of Python variables

vardumper.py

"""
The code is placed in to public domain by
anatoly techtonik <techtonik@gmail.com>

Produce readable representation of variable content,
including custom properties for complex objects.
Needed features:

[ ] easy import
[ ] sane defaults
  [ ] print to screen (stdout)
  [ ] don't show internal __ fields
  [ ] indent nested structures
[ ] detect loops
[ ] output to different stream with .write method
[ ] output to string
[ ] colorize if possible

"There should be one-- and preferably only one --obvious way to do it."
Methods.
https://stackoverflow.com/questions/192109/is-there-a-function-in-python-to-print-all-the-current-properties-and-values-of

1. print obj.__dict__
Advantages: returns key and value, which allows to inspect value directly.
Fail: Not all objects have __dict__ attribute, for example set.

2. print vars(obj)
Same fail as above. "TypeError: vars() argument must have __dict__ attribute".

3. print dir(obj)
Seems to always work (unless user botched __dir__ method in their class).
Returns only names, so need to make a separate lookup call [ ] to fetch
values and their types. The lookup call may trigger additional logic.

4. inspect.getmembers()
"""

import inspect
import sys

def dumpvar(obj, _indent=0, _writeto=sys.stdout):
    _writeto.write(' '*_indent + type(obj).__name__ + '\n')
    for name, value in inspect.getmembers(obj):
        # [x] filter standard __ symbols
        #   [ ] filter non-overriden __ symbols
        if not name.startswith('__'):
            _writeto.write(' '*(_indent+2) + name + '\n')