Agent skill
bio-phylo-tree-io
Read, write, and convert phylogenetic tree files using Biopython Bio.Phylo. Use when parsing Newick, Nexus, PhyloXML, or NeXML tree formats, converting between formats, or handling multiple trees.
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/data/tree-io
SKILL.md
Tree I/O
Parse, write, and convert phylogenetic tree files in various formats.
Required Import
from Bio import Phylo
from io import StringIO
Supported Formats
| Format | Extension | Description |
|---|---|---|
newick |
.nwk, .tre, .tree | Standard format with branch lengths |
nexus |
.nex, .nxs | Rich format with annotations (PAUP, MrBayes) |
phyloxml |
.xml | XML format with metadata support |
nexml |
.nexml | Modern XML format |
cdao |
.rdf | RDF format (limited use) |
Reading Trees
# Read single tree
tree = Phylo.read('tree.nwk', 'newick')
# Read multiple trees from file
trees = list(Phylo.parse('bootstrap_trees.nwk', 'newick'))
print(f'Loaded {len(trees)} trees')
# Read from string
tree_string = '((A:0.1,B:0.2):0.3,(C:0.4,D:0.5):0.6);'
tree = Phylo.read(StringIO(tree_string), 'newick')
# Read PhyloXML with metadata
tree = Phylo.read('annotated.xml', 'phyloxml')
# Read Nexus (often contains multiple trees)
trees = list(Phylo.parse('mrbayes.nex', 'nexus'))
Writing Trees
# Write single tree
Phylo.write(tree, 'output.nwk', 'newick')
# Write multiple trees
Phylo.write(trees, 'all_trees.nwk', 'newick')
# Write to PhyloXML (preserves metadata)
Phylo.write(tree, 'output.xml', 'phyloxml')
# Write to Nexus
Phylo.write(tree, 'output.nex', 'nexus')
Serialize to String
tree = Phylo.read('tree.nwk', 'newick')
# Get tree as string (useful for embedding, logging, or API responses)
newick_string = format(tree, 'newick')
print(newick_string) # ((A:0.1,B:0.2):0.3,(C:0.4,D:0.5):0.6);
# Alternative method
newick_string = tree.format('newick')
# Other formats work too
phyloxml_string = format(tree, 'phyloxml')
Format Conversion
# Direct file conversion
Phylo.convert('input.nwk', 'newick', 'output.xml', 'phyloxml')
Phylo.convert('mrbayes.nex', 'nexus', 'trees.nwk', 'newick')
# Convert with processing
tree = Phylo.read('input.nwk', 'newick')
tree.ladderize() # Sort branches
Phylo.write(tree, 'sorted.nwk', 'newick')
Quick Tree Inspection
tree = Phylo.read('tree.nwk', 'newick')
# Print ASCII representation
print(tree)
# ASCII tree diagram
Phylo.draw_ascii(tree)
# Basic tree properties
print(f'Total branch length: {tree.total_branch_length()}')
print(f'Number of terminals: {len(tree.get_terminals())}')
print(f'Is bifurcating: {tree.is_bifurcating()}')
Accessing Tree Structure
# Get all terminal (leaf) nodes
terminals = tree.get_terminals()
for term in terminals:
print(f'{term.name}: branch_length={term.branch_length}')
# Get all internal nodes
nonterminals = tree.get_nonterminals()
# Get all clades (nodes)
all_clades = list(tree.find_clades())
# Find specific clade by name
clade = tree.find_any(name='Human')
Tree from Newick String Patterns
# Simple tree (no branch lengths)
tree = Phylo.read(StringIO('((A,B),(C,D));'), 'newick')
# With branch lengths
tree = Phylo.read(StringIO('((A:0.1,B:0.2):0.3,(C:0.4,D:0.5):0.6);'), 'newick')
# With internal node names
tree = Phylo.read(StringIO('((A,B)AB,(C,D)CD)root;'), 'newick')
# With bootstrap values (internal node names)
tree = Phylo.read(StringIO('((A:0.1,B:0.2)95:0.3,(C:0.4,D:0.5)80:0.6);'), 'newick')
Working with PhyloXML Metadata
# PhyloXML supports rich annotations
tree = Phylo.read('annotated.xml', 'phyloxml')
for clade in tree.find_clades():
if clade.confidences:
print(f'{clade.name}: confidence={clade.confidences[0].value}')
if hasattr(clade, 'taxonomy') and clade.taxonomy:
print(f'{clade.name}: taxonomy={clade.taxonomy.scientific_name}')
# Convert Newick to PhyloXML (adds metadata capabilities)
newick_tree = Phylo.read('simple.nwk', 'newick')
phyloxml_tree = newick_tree.as_phyloxml()
Handling Multiple Trees
# Parse bootstrap or posterior trees
trees = list(Phylo.parse('bootstrap.nwk', 'newick'))
print(f'Loaded {len(trees)} bootstrap trees')
# Process each tree
for i, tree in enumerate(trees):
print(f'Tree {i}: {len(tree.get_terminals())} taxa')
# Write subset of trees
Phylo.write(trees[:100], 'first_100.nwk', 'newick')
Iterating Over Large Tree Files
# Memory-efficient iteration (doesn't load all trees at once)
for tree in Phylo.parse('large_file.nwk', 'newick'):
if tree.total_branch_length() > 1.0:
print(f'Long tree: {tree.total_branch_length()}')
Common Newick Format Variations
| Input | Description |
|---|---|
(A,B,C); |
Unrooted, no lengths |
((A,B),C); |
Rooted topology |
(A:0.1,B:0.2); |
With branch lengths |
((A,B)X,C); |
Internal node named X |
((A,B):0.5[90],C); |
Branch with bootstrap |
Error Handling
from Bio import Phylo
from io import StringIO
# Check for valid newick
tree_string = '((A,B),(C,D));'
try:
tree = Phylo.read(StringIO(tree_string), 'newick')
print('Valid tree')
except Exception as e:
print(f'Parse error: {e}')
# Handle missing branch lengths
tree = Phylo.read('tree.nwk', 'newick')
for clade in tree.find_clades():
if clade.branch_length is None:
clade.branch_length = 0.0 # Set default
Format-Specific Notes
| Format | Strengths | Limitations |
|---|---|---|
| Newick | Universal, simple | No metadata |
| Nexus | PAUP/MrBayes compatible | Complex syntax |
| PhyloXML | Rich metadata, colors | Verbose |
| NeXML | Modern, extensible | Less common |
Related Skills
- tree-visualization - Draw and export tree figures
- tree-manipulation - Root, prune, and modify tree structure
- distance-calculations - Compute distances and build trees from alignments
- alignment/alignment-io - Read MSA files for tree construction
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