# To collapse nodes in a tree¶

To collapse nodes, don’t do it this way:

```
for n in t.iterInternalsNoRoot():
t.collapseNode(n)
```

because it modifies the tree as it iterates, and so it does not work. Do it this way instead:

```
# First make a list of nodes that you want to collapse
toCollapse = [n for n in t.iterInternalsNoRoot()]
# Then collapse them
for n in toCollapse:
t.collapseNode(n)
```

Or perhaps more realistically:

```
toCollapse = [n for n in t.iterInternalsNoRoot() if n.br.support < 0.7]
for n in toCollapse:
t.collapseNode(n)
```