Re: iterating over DictRow

On 9/23/20 2:54 PM, Karsten Hilbert wrote:
> Dear all,
>
> I cannot currently wrap my head around why I am seeing this:
>
> 2020-09-23 23:30:23 gmConnectionPool.py::<module>() #87): psycopg2 module version: 2.8.5 (dt dec pq3 ext)
> 2020-09-23 23:30:23 gmConnectionPool.py::<module>() #88): PostgreSQL via DB-API module "<module 'psycopg2' from '/usr/lib/python3/dist-packages/psycopg2/__init__.py'>": API level 2.0, thread safety 2, parameter style "pyformat"
> 2020-09-23 23:30:23 gmConnectionPool.py::<module>() #89): libpq version (compiled in): 120002
> 2020-09-23 23:30:23 gmConnectionPool.py::<module>() #90): libpq version (loaded now) : 120004
> ...
> 2020-09-23 23:30:28 gmConnectionPool.py::__log_on_first_contact() #445): heed Prime Directive
> 2020-09-23 23:30:28 gmConnectionPool.py::__log_on_first_contact() #457): PostgreSQL version (numeric): 11.7
> ...
> 2020-09-23 23:31:02 gmMacro.py::_get_variant_diagnoses() #2442): [[260, 'L: Bewegungsapparat', False, 'B', 'clin.health_issue'], [260, 'K: aHT/HI', False, 'B', 'clin.health_issue'], [260, 'D: Verdauung', False, None, 'clin.health_issue']]
> 2020-09-23 23:31:02 gmMacro.py::_get_variant_diagnoses() #2443): <class 'psycopg2.extras.DictRow'>
> 2020-09-23 23:31:02 gmMacro.py::_escape_dict() #2851): 260
> 2020-09-23 23:31:02 gmMacro.py::__getitem__() #880): placeholder handling error: diagnoses:: \item %(diagnosis)s::
> Traceback (most recent call last):
> File "/home/ncq/Projekte/gm/git/gnumed/gnumed/Gnumed/wxpython/gmMacro.py", line 869, in __getitem__
> val = handler(data = options)
> File "/home/ncq/Projekte/gm/git/gnumed/gnumed/Gnumed/wxpython/gmMacro.py", line 2445, in _get_variant_diagnoses
> return '\n'.join(template % self._escape_dict(dx, none_string = '?', bool_strings = [_('yes'), _('no')]) for dx in selected)
> File "/home/ncq/Projekte/gm/git/gnumed/gnumed/Gnumed/wxpython/gmMacro.py", line 2445, in <genexpr>
> return '\n'.join(template % self._escape_dict(dx, none_string = '?', bool_strings = [_('yes'), _('no')]) for dx in selected)
> File "/home/ncq/Projekte/gm/git/gnumed/gnumed/Gnumed/wxpython/gmMacro.py", line 2852, in _escape_dict
> val = the_dict[field]
> File "/usr/lib/python3/dist-packages/psycopg2/extras.py", line 169, in __getitem__
> return super(DictRow, self).__getitem__(x)
> IndexError: list index out of range
>
> This line logs a list of DictRow's:
>
> 2020-09-23 23:31:02 gmMacro.py::_get_variant_diagnoses() #2442): [[260, 'L: Bewegungsapparat', False, 'B', 'clin.health_issue'], [260, 'K: aHT/HI', False, 'B', 'clin.health_issue'], [260, 'D: Verdauung', False, None, 'clin.health_issue']]
>
> as evidenced here:
>
> 2020-09-23 23:31:02 gmMacro.py::_get_variant_diagnoses() #2443): <class 'psycopg2.extras.DictRow'>
>
> The logging code:
>
> _log.debug('%s', selected)
> _log.debug('%s', type(selected[0]))
>
> and then iterates over the list of DictRow's as per list
> comprehension like so:
>
> return '\n'.join(template % self._escape_dict(dx, none_string = '?', bool_strings = [_('yes'), _('no')]) for dx in selected)
>
> where _escape_dict() does this:
>
> def _escape_dict(self, the_dict=None, date_format='%Y %b %d %H:%M', none_string='', bool_strings=None):
> data = {}
> for field in the_dict:
> _log.debug('%s', field)
> val = the_dict[field]
> if val is None:
> ...
> if isinstance(val, bool):
> ...
> if isinstance(val, datetime.datetime):
> ...
> if self.__esc_style in ['latex', 'tex']:
> ...
> elif self.__esc_style in ['xetex', 'xelatex']:
> ...
> return data
>
> Iterating over the_dict should work for lists (produces
> values) OR dicts (produces keys, under py3). It seems as if
> the line
>
> for field in the_dict: # I hoped to iterate over the keys = column names
>
> somehow "decides": "currently we are treating the_dict as a
> list (after all, it is a DictRow, which _can_ be treated as a
> list) which then "turns" the dict-style access in
>
> val = the_dict[field]
>
> into a list access.
>
> Somehow I have a feeling that due to the type of "field"
> -- it being integer (namely, a primary key) -- forces
>
> the_dict[field]
>
> to attempt a list-style index based access (which fails, due
> to there not being 260 columns in the SQL query result :-)
>
> Solutions that come to mind:
>
> _Must_ I use RealDictCursor() to safely avoid this trap ?
>
> (or else dict()ify DictRow's as needed)
>
> Any insights to be had ?

Maybe?:

con = psycopg2.connect("dbname=production host=localhost user=postgres",
cursor_factory=DictCursor)
cur = con.cursor()
cur.execute("select * from cell_per")

the_dict = cur.fetchall()

# Example 1

for row in the_dict:
for fld in row:
print(fld)

# Return just field values
...

4
HERB 3.5
19
None
2020-09-22 17:34:31
None
postgres
herb
none
HR3

#Example 2

for row in the_dict:
for fld in dict(row):
print(fld, row[fld])

Showing the field name and field value.
...
line_id 4
category HERB 3.5
cell_per 19
ts_insert None
ts_update 2020-09-22 17:34:31
user_insert None
user_update postgres
plant_type herb
season none
short_category HR3

>
> Thanks,
> Karsten
> --
> GPG 40BE 5B0E C98E 1713 AFA6 5BC0 3BEA AC80 7D4F C89B
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com