can access RRD using BASH but not using PYTHON

[sebastianet]

Hi. I can access the same RRD using Bash code (1-bellow) but no using python (2-bellow).
I am using "RRDtool 1.7.1" with "Python 2.7.16" under Raspberry "Raspbian GNU/Linux 10 (buster)"
Any ideas ?

=== (1) bash ===

rrdtool xport                                        \
        --start now-1min --end now        \
        --step 5  --json   -t                       \
        DEF:xx=../pkw.rrd:Pprod:MAX    \
        XPORT:xx 

===

Output is :

===

{ "about": "RRDtool graph JSON output",
  "meta": {
    "start": 1652807370,
    "end": 1652807425,
    "step": 5,
    "legend": [
      ""
          ]
     },
  "data": [
    [ "1652807370",9.745446652e+02 ],
    [ "1652807375",9.754641829e+02 ],

===

=== (2) python ===

rrdtool.xport ( '--start', 'now-1min',
                      '--end',   'now',
                      '--step',  '5',
                      '--json',
                      '-t',
                      'DEF:xx=../pkw.rrd:Pprod:MAX',
                      'XPORT:xx' )
```===

*** NO OUTPUT AT ALL, no error ***