如何消除Python Diagrams中Cluster内节点的多余间距？

你用以下代码生成Cluster时，节点A、B、C、D之间出现了大量不必要的间距：

from diagrams import Diagram, Cluster, Node

with Diagram('./output/output', show=False, outformat='svg') as d:
        with Cluster('cluster'):
            n1 = Node('A', height = '0.5', width = '5', labelloc = "c", fillcolor = 'purple', fontcolor = 'white', style = 'filled')
            n2 = Node('B', height = '0.5', width = '5', labelloc = "c", fillcolor = 'purple', fontcolor = 'white', style = 'filled')
            n3 = Node('C', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')
            n4 = Node('D', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')

这是因为Diagrams依赖的Graphviz默认布局会给节点预留间距，你可以通过以下几种方式消除这些间距：

方法一：调整Cluster的全局间距属性 #

直接在Cluster中设置Graphviz的ranksep（同层级节点垂直间距）和nodesep（节点水平间距）参数，数值越小间距越紧凑：

from diagrams import Diagram, Cluster, Node

with Diagram('./output/output', show=False, outformat='svg') as d:
    # 在Cluster里添加graph_attr参数控制间距
    with Cluster('cluster', graph_attr={"ranksep": "0.1", "nodesep": "0.1"}):
        n1 = Node('A', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')
        n2 = Node('B', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')
        n3 = Node('C', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')
        n4 = Node('D', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')

方法二：更换布局引擎 #

默认的dot布局会预留较多间距，换成neato或fdp这类更紧凑的布局引擎，能自动缩小节点间距：

from diagrams import Diagram, Cluster, Node

# 在Diagram中指定engine参数为neato
with Diagram('./output/output', show=False, outformat='svg', engine="neato") as d:
    with Cluster('cluster'):
        n1 = Node('A', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')
        n2 = Node('B', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')
        n3 = Node('C', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')
        n4 = Node('D', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')

方法三：用隐形边强制缩小间距 #

如果是垂直排列的节点间距过大，可以给节点添加隐形边，并设置边的长度参数len，手动控制间距：

from diagrams import Diagram, Cluster, Node

with Diagram('./output/output', show=False, outformat='svg') as d:
    with Cluster('cluster'):
        n1 = Node('A', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')
        n2 = Node('B', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')
        n3 = Node('C', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')
        n4 = Node('D', height='0.5', width='5', labelloc="c", fillcolor='purple', fontcolor='white', style='filled')
        # 设置边的长度为0.1，缩小节点间垂直间距
        n1 >> {"len": "0.1"} >> n2
        n2 >> {"len": "0.1"} >> n3
        n3 >> {"len": "0.1"} >> n4

内容的提问来源于stack exchange，提问作者Epsi95