Error on adding a row to an empty DataFrame

[paulburt]

Environment

• Operating System: Linux

• Python Version: $ python --version Python 2.7.12

• How did you install Qgrid: (pip, conda, or other (please explain)) pip install qgrid jupyter nbextension enable --py --sys-prefix qgrid jupyter nbextension enable --py --sys-prefix widgetsnbextension

• Python packages: $ pip freeze or $ conda list (please include qgrid, notebook, and jupyterlab versions) backports-abc==0.5 backports.shutil-get-terminal-size==1.0.0 bleach==2.1.4 configparser==3.5.0 decorator==4.3.0 defusedxml==0.5.0 entrypoints==0.2.3 enum34==1.1.6 functools32==3.2.3.post2 futures==3.2.0 html5lib==1.0.1 ipaddress==1.0.22 ipykernel==4.9.0 ipython==5.8.0 ipython-genutils==0.2.0 ipywidgets==7.4.2 Jinja2==2.10 jsonschema==2.6.0 jupyter-client==5.2.3 jupyter-core==4.4.0 MarkupSafe==1.0 mistune==0.8.3 nbconvert==5.4.0 nbformat==4.4.0 notebook==5.6.0 numpy==1.15.1 pandas==0.23.4 pandocfilters==1.4.2 pathlib2==2.3.2 pexpect==4.6.0 pickleshare==0.7.4 pkg-resources==0.0.0 prometheus-client==0.3.1 prompt-toolkit==1.0.15 ptyprocess==0.6.0 Pygments==2.2.0 python-dateutil==2.7.3 pytz==2018.5 pyzmq==17.1.2 qgrid==1.1.1 scandir==1.9.0 Send2Trash==1.5.0 simplegeneric==0.8.1 singledispatch==3.4.0.3 six==1.11.0 terminado==0.8.1 testpath==0.3.1 tornado==5.1.1 traitlets==4.3.2 wcwidth==0.1.7 webencodings==0.5.1 widgetsnbextension==3.4.2

• Jupyter lab packages (if applicable): $ jupyter labextension list

Description of Issue

Adding rows to the empty DataFrame does not work

• What did you expect to happen? A new cell or an error message appears
• What happened instead? 'Add Row' button stays greyed out, jupyter console reads [IPKernelApp] ERROR | max() arg is an empty sequence [IPKernelApp] ERROR | Unhandled exception while handling msg Traceback (most recent call last): File "/home/pb/play/jupyter/jupyter-venv/local/lib/python2.7/site-packages/qgrid/grid.py", line 1419, in _handle_qgrid_msg self._handle_qgrid_msg_helper(content) File "/home/pb/play/jupyter/jupyter-venv/local/lib/python2.7/site-packages/qgrid/grid.py", line 1483, in _handle_qgrid_msg_helper row_index = self._duplicate_last_row() File "/home/pb/play/jupyter/jupyter-venv/local/lib/python2.7/site-packages/qgrid/grid.py", line 1641, in _duplicate_last_row last_index = max(df.index) ValueError: max() arg is an empty sequence

Reproduction Steps

1.Create a four-cell jupyter notebook with the contents below and run it

2. Press 'Add Row' button

import pandas as pd import qgrid

df = pd.DataFrame({'a':['b']}) #Add Row works

df = pd.DataFrame() #Add Row does not work qgrid.show_grid(df,show_toolbar=True)

What steps have you taken to resolve this already?

...

Anything else?

...

[DancingQuanta]

Similar to using qgrid_widget.add_row() for an empty dataframe.

[LukaPitamic]

same here :(

[AlJohri]

same here

[IPKernelApp] ERROR | max() arg is an empty sequence
[IPKernelApp] ERROR | Unhandled exception while handling msg
Traceback (most recent call last):
  File "/Users/johria/Development/dad-pdf-extraction/.venv/lib/python3.7/site-packages/qgrid/grid.py", line 1419, in _handle_qgrid_msg
    self._handle_qgrid_msg_helper(content)
  File "/Users/johria/Development/dad-pdf-extraction/.venv/lib/python3.7/site-packages/qgrid/grid.py", line 1483, in _handle_qgrid_msg_helper
    row_index = self._duplicate_last_row()
  File "/Users/johria/Development/dad-pdf-extraction/.venv/lib/python3.7/site-packages/qgrid/grid.py", line 1641, in _duplicate_last_row
    last_index = max(df.index)
ValueError: max() arg is an empty sequence

[LukaPitamic]

@AlJohri - I solved the problem by adding one dummy row to pandas data frame before QGrid gets instantiated. Also, I noticed having DateTime as Index type represents a lot of challenges to QGrid. Using "Int64" type of Index, and separate (non index) column of DateTime type solves it all in one swoop. Not ideal solution, but next best ;)

[wuyuanyi135]

This issue is still present in 1.3.1