How to customize datetime ticks in Plotly (Python)

šŸ“Š Plotly Python
1

Hi there!
So Iā€™ve created a gantt chart with Plotlyā€™s Dash and Iā€™d be quite happy, if it werenā€™t for the x axis ticks.

Hereā€™s the chart:

one
one1345Ɨ526 10.9 KB

Nice, but for the x axis ticks. Iā€™d like to customize them to fit my needs:

  1. Iā€™d like them to start on a monday (04 Jan), instead of a sunday (10 Jan) and continue week-wise as they already do

  2. Instead of ā€œ04 Janā€, the tick labels should be something like this: ā€œKW: 01 ('21)ā€. Here, KW is supposed to mean calendar week.

  3. I donā€™t want to show every tick label. Itā€™d be nice if the chart only shows every first KW of a year and every fifth

So, I was looking for a way to do this and found in Plotly Layout References (xaxis-tickvals) that thereā€™s supposed to be a smooth way to do so. I just need a list of tickvals for the locations in the chart and a list of ticktext for the labels and need to set tickmode to ā€˜arrayā€™.

As my code is too long, Iā€™ll just provide a little example. Letā€™s say this is my code:

import plotly.figure_factory as ff
import datetime

df = [dict(Task="Job A", Start='2021-01-08', Finish='2021-01-29'),
  dict(Task="Job B", Start='2021-01-15', Finish='2021-02-12'),
  dict(Task="Job C", Start='2021-01-29', Finish='2021-02-19'),
  dict(Task="Job D", Start='2021-02-05', Finish='2021-02-26')]

my_figure = ff.create_gantt(df, showgrid_x=True, showgrid_y=True)
weeks_ticktext = ['KW: 01 (\'21)', '', '', '', 'KW: 05 (\'21)', '', '', '', '']
weeks_tickvals = [datetime.datetime(2021, 1, 4, 0, 0), datetime.datetime(2021, 1, 11, 0, 0),
              datetime.datetime(2021, 1, 18, 0, 0), datetime.datetime(2021, 1, 25, 0, 0),
              datetime.datetime(2021, 2, 1, 0, 0), datetime.datetime(2021, 2, 8, 0, 0),
              datetime.datetime(2021, 2, 15, 0, 0), datetime.datetime(2021, 2, 22, 0, 0),
              datetime.datetime(2021, 3, 1, 0, 0)]
my_figure.layout.xaxis['tickmode'] = 'array'
my_figure.layout.xaxis['tickvals'] = weeks_tickvals
my_figure.layout.xaxis['ticktext'] = weeks_ticktext
my_figure.show()

Then, this code will produce the following graph:

two
two1868Ɨ609 6.25 KB

Now, I donā€™t understand why the x axis didnā€™t start and didnā€™t get displayed the way I wanted them to be.

I am thankful for any help!

NOTE: I already asked the same question in stackoverflow here