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Python

#!/usr/bin/env python3
"""Extract a Python project's class-inheritance graph as autolayout graph JSON.
A finer-grained companion to pyimports.py: instead of module->module imports,
it emits one node per class and an edge from each subclass to the project base
classes it extends. With --group, classes are boxed by their module (nested by
sub-package), so the result reads as an auto-generated class hierarchy.
python3 pyclasses.py myproject --group -o graph.json
python3 autolayout.py graph.json -o diagram.drawio
Only inheritance is resolved (statically reliable); base classes are matched
by name, preferring a class in the same module. External bases (object,
Exception, third-party) are ignored. This is a *class structure* view, not a
function-level call graph — static call resolution in Python is unreliable, so
that is deliberately out of scope.
Usage: python3 pyclasses.py <project_dir> [-o graph.json] [--direction TB|LR]
[--group] [--no-reduce]
"""
import argparse
import ast
import json
import os
import re
import subprocess
import sys
def discover(root):
"""Map dotted module name -> file path; qualify with the package name when
root is itself a package (mirrors pyimports.py)."""
root = os.path.abspath(root)
base = os.path.basename(root) if os.path.exists(os.path.join(root, "__init__.py")) else ""
modules = {}
for dirpath, _, files in os.walk(root):
for fn in files:
if not fn.endswith(".py"):
continue
rel = os.path.relpath(os.path.join(dirpath, fn), root)[:-3]
parts = rel.split(os.sep)
if parts[-1] == "__init__":
parts = parts[:-1]
parts = ([base] + parts) if base else parts
if parts:
modules[".".join(parts)] = os.path.join(dirpath, fn)
return modules, base
def base_name(node):
"""Simple name of a base-class expression (`Foo` or `pkg.Foo` -> 'Foo')."""
if isinstance(node, ast.Name):
return node.id
if isinstance(node, ast.Attribute):
return node.attr
return None
def classes_in(module, path):
"""Top-level classes of a module: list of (qualified_id, simple_name, [base names])."""
try:
with open(path, encoding="utf-8") as f:
tree = ast.parse(f.read(), filename=path)
except SyntaxError:
return []
out = []
for node in tree.body:
if isinstance(node, ast.ClassDef):
bases = [b for b in (base_name(b) for b in node.bases) if b]
out.append((f"{module}.{node.name}", node.name, bases))
return out
def transitive_reduce(nodes, edges):
"""Drop edges implied by a longer path, via Graphviz `tred`."""
idx = {n: i for i, n in enumerate(nodes)}
dot = "digraph{" + "".join(f"{idx[s]}->{idx[t]};" for s, t in edges) + "}"
try:
out = subprocess.run(["tred"], input=dot, capture_output=True,
text=True, check=True).stdout
except (FileNotFoundError, subprocess.CalledProcessError) as exc:
sys.stderr.write(f"warning: tred unavailable, keeping all edges ({exc})\n")
return edges
rev = {i: n for n, i in idx.items()}
return [(rev[int(a)], rev[int(b)]) for a, b in re.findall(r"(\d+)\s*->\s*(\d+)", out)]
def main():
ap = argparse.ArgumentParser(description="Python class-inheritance graph -> autolayout graph JSON.")
ap.add_argument("project", help="package or project directory")
ap.add_argument("-o", "--output", help="output JSON path (default: stdout)")
ap.add_argument("--direction", default="TB", choices=["TB", "LR"])
ap.add_argument("--group", action="store_true",
help="box classes by their module (nested by sub-package)")
ap.add_argument("--no-reduce", action="store_true",
help="keep every edge (skip transitive reduction)")
args = ap.parse_args()
modules, base = discover(args.project)
classes = {} # qualified id -> (module, bases)
by_name = {} # simple name -> [qualified ids]
for mod, path in modules.items():
for cid, name, bases in classes_in(mod, path):
classes[cid] = (mod, bases)
by_name.setdefault(name, []).append(cid)
if not classes:
sys.exit(f"error: no classes found under {args.project}")
def resolve(name, module):
cands = by_name.get(name, [])
same = [c for c in cands if classes[c][0] == module]
if same:
return same[0] # prefer a class in the same module
return cands[0] if len(cands) == 1 else None # else only if unambiguous
edges = set()
for cid, (mod, bases) in classes.items():
for b in bases:
target = resolve(b, mod)
if target and target != cid:
edges.add((cid, target))
edges = sorted(edges)
raw = len(edges)
if not args.no_reduce:
edges = transitive_reduce(list(classes), edges)
strip = base + "." if base else ""
short = lambda m: m[len(strip):] if strip and m.startswith(strip) else m
def node(cid):
# No hard-coded colour: autolayout tints nodes by their group (module),
# so a grouped class hierarchy reads as coloured-by-module.
d = {"id": cid, "label": cid.rsplit(".", 1)[1]}
if args.group:
mod = classes[cid][0]
path = short(mod).replace(".", "/") # module path -> nested boxes
if path:
d["group"] = path
return d
graph = {
"direction": args.direction,
"nodes": [node(cid) for cid in classes],
"edges": [{"source": s, "target": t} for s, t in edges],
}
text = json.dumps(graph, indent=2)
if args.output:
with open(args.output, "w", encoding="utf-8") as f:
f.write(text)
sys.stderr.write(f"wrote {args.output}\n")
else:
sys.stdout.write(text)
note = "" if args.no_reduce else f" (reduced from {raw})"
sys.stderr.write(f"{len(classes)} classes, {len(edges)} inheritance edges{note}\n")
if __name__ == "__main__":
main()