如何在单个浏览器页面上向 Dash 应用程序添加多个图形？

Question

如何在同一页面上添加多个图片显示在图片中？我正在尝试将 html.Div 组件添加到以下代码以更新页面布局以在单个页面上添加更多图表，但这些新添加的图表不会显示在页面上，图片中仅显示旧图表可见的。我应该修改什么元素，比如说在浏览器上的 dash 应用程序的单个页面上添加上传图像中显示的图形 3 次？


import dash
import dash_core_components as dcc
import dash_html_components as html
i[enter image description here][1]mport plotly.express as px
import pandas as pd

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

# assume you have a "long-form" data frame
# see https://plotly.com/python/px-arguments/ for more options
df = pd.DataFrame({
    "Fruit": ["Apples", "Oranges", "Bananas", "Apples", "Oranges", "Bananas"],
    "Amount": [4, 1, 2, 2, 4, 5],
    "City": ["SF", "SF", "SF", "Montreal", "Montreal", "Montreal"]
})

fig = px.bar(df, x="Fruit", y="Amount", color="City", barmode="group")

app.layout = html.Div(children=[
    html.H1(children='Hello Dash'),

    html.Div(children='''
        Dash: A web application framework for Python.
    '''),

    dcc.Graph(
        id='example-graph',
        figure=fig
    )
])

if __name__ == '__main__':
    app.run_server(debug=True)

Answer 1

要多次添加相同的图形，您只需要扩展您的 app.layout。我在下面扩展了你的代码作为例子。

import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output
import pandas as pd
import plotly.express as px

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

# assume you have a "long-form" data frame
# see https://plotly.com/python/px-arguments/ for more options
df_bar = pd.DataFrame({
    "Fruit": ["Apples", "Oranges", "Bananas", "Apples", "Oranges", "Bananas"],
    "Amount": [4, 1, 2, 2, 4, 5],
    "City": ["SF", "SF", "SF", "Montreal", "Montreal", "Montreal"]
})

fig = px.bar(df_bar, x="Fruit", y="Amount", color="City", barmode="group")

app.layout = html.Div(children=[
    # All elements from the top of the page
    html.Div([
        html.H1(children='Hello Dash'),

        html.Div(children='''
            Dash: A web application framework for Python.
        '''),

        dcc.Graph(
            id='graph1',
            figure=fig
        ),  
    ]),
    # New Div for all elements in the new 'row' of the page
    html.Div([
        html.H1(children='Hello Dash'),

        html.Div(children='''
            Dash: A web application framework for Python.
        '''),

        dcc.Graph(
            id='graph2',
            figure=fig
        ),  
    ]),
])

if __name__ == '__main__':
    app.run_server(debug=True)

我构建布局的方式是嵌套 html.Div 组件。对于每个图形和相应的标题、文本等，我们制作另一个 html.Div，在我们的应用程序中制作一个新的 'row'。

要记住的一件事是不同的组件需要唯一的 ID。在此示例中，我们将同一个图表显示两次，但它们并不完全相同 object。我们正在使用相同的 plotly.express 图

制作两个 dcc.Graph object

我已经为你做了另一个例子，我添加了另一个数字动态。每次从下拉菜单中选择新的色标时，第二个数字都会更新。这就是 Dash 的真正潜力所在。您可以在 tutorial

中阅读有关回调函数的更多信息

import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output
import pandas as pd
import plotly.express as px

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

# assume you have a "long-form" data frame
# see https://plotly.com/python/px-arguments/ for more options
df_bar = pd.DataFrame({
    "Fruit": ["Apples", "Oranges", "Bananas", "Apples", "Oranges", "Bananas"],
    "Amount": [4, 1, 2, 2, 4, 5],
    "City": ["SF", "SF", "SF", "Montreal", "Montreal", "Montreal"]
})

fig = px.bar(df_bar, x="Fruit", y="Amount", color="City", barmode="group")

# Data for the tip-graph
df_tip = px.data.tips()

app.layout = html.Div(children=[
    # All elements from the top of the page
    html.Div([
        html.H1(children='Hello Dash'),

        html.Div(children='''
            Dash: A web application framework for Python.
        '''),

        dcc.Graph(
            id='example-graph',
            figure=fig
        ),  
    ]),
    # New Div for all elements in the new 'row' of the page
    html.Div([ 
        dcc.Graph(id='tip-graph'),
        html.Label([
            "colorscale",
            dcc.Dropdown(
                id='colorscale-dropdown', clearable=False,
                value='bluyl', options=[
                    {'label': c, 'value': c}
                    for c in px.colors.named_colorscales()
                ])
        ]),
    ])
])

# Callback function that automatically updates the tip-graph based on chosen colorscale
@app.callback(
    Output('tip-graph', 'figure'),
    [Input("colorscale-dropdown", "value")]
)
def update_tip_figure(colorscale):
    return px.scatter(
        df_color, x="total_bill", y="tip", color="size",
        color_continuous_scale=colorscale,
        render_mode="webgl", title="Tips"
    )

if __name__ == '__main__':
    app.run_server(debug=True)

您的下一个问题可能是，如何并排放置多个图形？这就是 CSS 和样式表很重要的地方。

您已经添加了一个外部样式表 https://codepen.io/chriddyp/pen/bWLwgP.css，这使我们能够使用 divs 的 className 组件更好地构造我们的布局。

无论屏幕大小，网页的宽度都设置为 12 列。所以如果我们想并排放置两个图形，每个图形占据屏幕的 50%，则每个图形需要填充 6 列。

我们可以通过嵌套另一个 html.Div 作为我们的上半行来实现这一点。在这个upperdiv中我们可以有另外两个divs，其中我们根据类名six columns指定样式。这将第一行分成两半

import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output
import pandas as pd
import plotly.express as px
from jupyter_dash import JupyterDash

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

# assume you have a "long-form" data frame
# see https://plotly.com/python/px-arguments/ for more options
df_bar = pd.DataFrame({
    "Fruit": ["Apples", "Oranges", "Bananas", "Apples", "Oranges", "Bananas"],
    "Amount": [4, 1, 2, 2, 4, 5],
    "City": ["SF", "SF", "SF", "Montreal", "Montreal", "Montreal"]
})

fig = px.bar(df_bar, x="Fruit", y="Amount", color="City", barmode="group")

app.layout = html.Div(children=[
    # All elements from the top of the page
    html.Div([
        html.Div([
            html.H1(children='Hello Dash'),

            html.Div(children='''
                Dash: A web application framework for Python.
            '''),

            dcc.Graph(
                id='graph1',
                figure=fig
            ),  
        ], className='six columns'),
        html.Div([
            html.H1(children='Hello Dash'),

            html.Div(children='''
                Dash: A web application framework for Python.
            '''),

            dcc.Graph(
                id='graph2',
                figure=fig
            ),  
        ], className='six columns'),
    ], className='row'),
    # New Div for all elements in the new 'row' of the page
    html.Div([
        html.H1(children='Hello Dash'),

        html.Div(children='''
            Dash: A web application framework for Python.
        '''),

        dcc.Graph(
            id='graph3',
            figure=fig
        ),  
    ], className='row'),
])

if __name__ == '__main__':
    app.run_server(debug=True)

如何在单个浏览器页面上向 Dash 应用程序添加多个图形？

How to add multiple graphs to Dash app on a single browser page?

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