Populate plotly.go.Figure['data']

fig_data.py

#1 Assign color to each unique item
from random import sample

colors = {item: 'rgb({}, {}, {})'.format(*sample(range(256), 3)) for item in data['Item'].unique()}
data['color'] = data['Item'].map(colors)

#2 Slice data, select earliest date available

##2.1 Select earliest year available 
frame1 = data[data['Year'] == data['Year'].min()]

##2.2 Sort the data by value and get the top 10 entries
top_entries = 10 # modify to get top 5, top 20 or any other
frame1 = frame1.sort_values('Value', ascending = False).iloc[:top_entries, :]

##2.3 Sort values in ascending order so that top bar corresponds to greatest value
frame1 = frame1.sort_values('Value', ascending = True)

#3 Populate data entry in plotly figure with frame1
fig['data'] = go.Bar(
  x = frame1['Value'],
  y = frame1['Item'],
  marker_color = frame1['color'],
  hoverinfo = 'all', # display Item name and Value when hovering over bar
  textposition = 'outside', # position text outside bar
  texttemplate = '%{y}<br>%{x:.4s}', # display y field (Item name), line break and then the value with up to 4 digits
  orientation = 'h' # to have bar growing rightwards
)