plotly-express 图形颜色图例应仅显示整数值

Question

使用 choropleth map 使用 plotly express 创建的图表显示了与意大利地区相关的 count 值的分布：

import pandas as pd
import requests
import plotly.express as px

data = {'regions' : ['Piemonte', 'Trentino-Alto Adige', 'Lombardia', 'Puglia', 'Basilicata', 
           'Friuli Venezia Giulia', 'Liguria', "Valle d'Aosta", 'Emilia-Romagna',
           'Molise', 'Lazio', 'Veneto', 'Sardegna', 'Sicilia', 'Abruzzo',
           'Calabria', 'Toscana', 'Umbria', 'Campania', 'Marche'],
        'counts' : [3, 3, 4, 2, 0,
                    4, 4, 0, 0,
                    1, 1, 0, 3, 4, 4,
                    3, 4, 3, 2, 4]}

df = pd.DataFrame.from_dict(data)

# Read the geojson data with Italy's regional borders [enter image description here][2]from github
repo_url = 'https://gist.githubusercontent.com/datajournalism-it/48e29e7c87dca7eb1d29/raw/2636aeef92ba0770a073424853f37690064eb0ea/regioni.geojson'
italy_regions_geo = requests.get(repo_url).json()

fig = px.choropleth(data_frame=df, 
                    geojson=italy_regions_geo, 
                    locations='regions', # name of dataframe column matching the region names
                    featureidkey='properties.NOME_REG',  # path to field in GeoJSON feature object with which to match the values passed in to locations
                    color='counts',
                    color_continuous_scale="Magma",
                    scope="europe",
                   )
fig.update_geos(resolution=50, 
                showcountries=False, 
                showcoastlines=False, 
                fitbounds="locations",
                showland=False)

fig.update_layout(margin={"r":0,"t":0,"l":0,"b":0})
fig.show()
fig.write_image("./italy.png")

当 count 的最大值为四时，图形颜色图例将包含带有小数点的标签，这是不需要的，因为值应被视为整数。一旦 count 的最大值为 5 或更大，小数点就会消失。如何控制图形颜色图例中小数点的出现？

Answer 1

此处记录https://plotly.com/python/reference/layout/coloraxis/#layout-coloraxis-colorbar-dtick
因此下面有一个额外的布局说明

import pandas as pd
import requests
import plotly.express as px

data = {'regions' : ['Piemonte', 'Trentino-Alto Adige', 'Lombardia', 'Puglia', 'Basilicata', 
           'Friuli Venezia Giulia', 'Liguria', "Valle d'Aosta", 'Emilia-Romagna',
           'Molise', 'Lazio', 'Veneto', 'Sardegna', 'Sicilia', 'Abruzzo',
           'Calabria', 'Toscana', 'Umbria', 'Campania', 'Marche'],
        'counts' : [3, 3, 4, 2, 0,
                    4, 4, 0, 0,
                    1, 1, 0, 3, 4, 4,
                    3, 4, 3, 2, 4]}

df = pd.DataFrame.from_dict(data)

# Read the geojson data with Italy's regional borders [enter image description here][2]from github
repo_url = 'https://gist.githubusercontent.com/datajournalism-it/48e29e7c87dca7eb1d29/raw/2636aeef92ba0770a073424853f37690064eb0ea/regioni.geojson'
italy_regions_geo = requests.get(repo_url).json()

fig = px.choropleth(data_frame=df, 
                    geojson=italy_regions_geo, 
                    locations='regions', # name of dataframe column matching the region names
                    featureidkey='properties.NOME_REG',  # path to field in GeoJSON feature object with which to match the values passed in to locations
                    color='counts',
                    color_continuous_scale="Magma",
                    scope="europe",
                   )
fig.update_geos(resolution=50, 
                showcountries=False, 
                showcoastlines=False, 
                fitbounds="locations",
                showland=False)

fig.update_layout(margin={"r":0,"t":0,"l":0,"b":0})
fig.update_layout(coloraxis={"colorbar":{"dtick":1}})
fig.show()

plotly-express 图形颜色图例应仅显示整数值

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