debtree to show debian package dependencies, inspired by pactree

debtree.py

#!/usr/bin/env python3
# show deb package dependency tree

import subprocess

INDENT = "  "
DPCONT = "│ "
DPMORE = "├─"
DPLAST = "└─"
#DPCONT = "  "
#DPMORE = ""
#DPLAST = ""
#DPCONT = "| "
#DPMORE = "+-"
#DPLAST = "`-"

NEXTINDENT = INDENT * 2
NEXTCONTIN = DPCONT + INDENT

RDEP = "apt-rdepends"



def get_deplist(pkg):
    return subprocess.run((RDEP, pkg), capture_output=True, text=True).stdout.split('\n')


parsetree = []
parsed = {}
def parse_deplist(pkg, deplist):

    def tree_for_el(el, seen=[]):
        if el in seen:
            return (el + ' ^', [])
        seen.append(el)
        return (el, [tree_for_el(d) for d in parsed[el]])

    def dependents(ilines):
        d = []
        for l in ilines:
            kw = l.split()
            if not kw or kw[0] != 'Depends:':
                break
            d.append(kw[1])
        return l, d

    parsed.clear()
    del parsetree[:]
    ideplist = iter(deplist)

    # skip intro
    while True:
        l = next(ideplist)
        if not l or l.startswith(pkg):
            break

    # process the list
    while l:
        nextl, deps = dependents(ideplist)
        parsed[l] = deps
        l = nextl

    parsetree.append(tree_for_el(pkg))


def output_tree():
    def output_key(key, deps, last=[]):
        if last:
            indent = INDENT + ''.join(NEXTINDENT if l else NEXTCONTIN for l in last[:-1])
            leader = DPLAST if last[-1] else DPMORE
        else:
            indent = ''
            leader = ''
        myline = ["%s%s%s" % (indent, leader, key)]
        for d in (output_key(k, d, last=last+[(k,d)==deps[-1]]) for k, d in deps):
            myline.extend(d)
        return myline
    return output_key(parsetree[0][0], parsetree[0][1])




if __name__ == "__main__":
    import sys

    if len(sys.argv) != 2:
      print('Usage: %s <package>' % sys.argv[0])
      sys.exit(1)

    try:
        deplist = get_deplist(sys.argv[1])
    except FileNotFoundError as e:
        print("Requires %s: %s" % (RDEP, e))
        sys.exit(1)
    parse_deplist(sys.argv[1], deplist)
    #print(parsed); print(parsetree); return
    print('\n'.join(output_tree()))

    sys.exit(0)