How to make bar plot in plotly with two categories?

It seems to me that the most flexible way would be to use go.Figure() and then

fig.add_traces(go.Bar(x=dfp['week'], y = dfp['cnt'], name = v))

for each value, v, in ['conversion - classic', 'conversion - modern', 'exit - classic', 'exit - modern'] like this:

fig = go.Figure()
for v in df['value'].unique():
    dfp = df[df['value']==v]
    fig.add_traces(go.Bar(x=dfp['week'], y = dfp['cnt'], name = v))
fig.update_layout(barmode='stack', template='plotly_dark')
fig.show()

Plot:

As far as I can tell, this should resemble your Excel output pretty closely.

Complete code:

import pandas as pd
import plotly.graph_objects as go
import plotly.express as px

df = pd.DataFrame(
dict(
    week=[1, 1, 2, 2, 3, 3] * 2,
    layout=["classic", "classic", "modern", "modern"] * 3,
    response=["conversion", "exit"] * 6,
    cnt=[26, 23, 45, 34, 55, 44, 53, 27, 28, 25, 30, 34],))

df['value'] = df['response'] + ' - ' + df['layout']
df = df.sort_values('value')
# df2 = df.groupby(['value', 'week']).sum().reset_index().sort_values('value')

fig = go.Figure()
for v in df['value'].unique():
    dfp = df[df['value']==v]
    fig.add_traces(go.Bar(x=dfp['week'], y = dfp['cnt'], name = v))
fig.update_layout(barmode='stack', template='plotly_dark')
fig.show()