Commented pretty-printer

pretty.py

def commented_pprint(obj, name='obj', indent=4):
    """
    Pretty-print object obj, which can contain nested dictionaries, lists and tuples,
    with comment lines showing how to index it.
    """
    pairs = list(_yield_pprint_lines(obj, name=name, indent=indent))
    max_len = max(len(line) for line, _ in pairs)    
    for line, comment in pairs:
        print(f'{line:{max_len}}  {comment}')

    
def _yield_pprint_lines(obj, name, indent, _this_indent=0, _top=True, _prefix=''):

    spaces = ' ' * _this_indent
    items = None

    is_dict = False
    if isinstance(obj, dict):
        chars = '{}'
        items = obj.items()
        is_dict = True
    elif isinstance(obj, tuple):
        chars = '()'
        items = enumerate(obj)
    elif isinstance(obj, list):
        chars = '[]'
        items = enumerate(obj)

    comma = '' if _top else ','
        
    if items is None:
        yield (f'{spaces}{_prefix}{repr(obj)}{comma}', f'# {name}')
    elif not obj:
        yield (f'{spaces}{_prefix}{chars}{comma}', f'# {name}')        
    else:
        yield (f'{spaces}{_prefix}{chars[0]}', '')
        for k, v in items:
            yield from _yield_pprint_lines(v,
                                           name=f'{name}[{repr(k)}]',
                                           indent=indent,
                                           _this_indent=(_this_indent + indent + len(_prefix)),
                                           _prefix=(f'{repr(k)}: ' if is_dict else ''),
                                           _top=False)
        yield (f"{spaces}{' ' * len(_prefix)}{chars[1]}{comma}", f'# {name}')



if __name__ == '__main__':
        
    a = { 'blah': ['foo', {'bar': 'baz', 'qux': 4}, 4, [], ['x', 6]], 'quux': [(3, 5), 's'] }
    commented_pprint(a, name='a')

    # PRINTS:
    #      
    #  {                                  
    #      'blah': [                      
    #                  'foo',             # a['blah'][0]
    #                  {                  
    #                      'bar': 'baz',  # a['blah'][1]['bar']
    #                      'qux': 4,      # a['blah'][1]['qux']
    #                  },                 # a['blah'][1]
    #                  4,                 # a['blah'][2]
    #                  [],                # a['blah'][3]
    #                  [                  
    #                      'x',           # a['blah'][4][0]
    #                      6,             # a['blah'][4][1]
    #                  ],                 # a['blah'][4]
    #              ],                     # a['blah']
    #      'quux': [                      
    #                  (                  
    #                      3,             # a['quux'][0][0]
    #                      5,             # a['quux'][0][1]
    #                  ),                 # a['quux'][0]
    #                  's',               # a['quux'][1]
    #              ],                     # a['quux']
    #  }                                  # a
    #