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
dxin 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
dxin 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
inselected)
 
> 
> 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.klaver@aklaver.com