--- a/python/safe.py	Wed May 26 13:52:53 2021 -0400
+++ b/python/safe.py	Thu May 27 06:09:01 2021 -0400
@@ -3,23 +3,26 @@
 import sys, math
 
 from util import *
-from bisect import insort_left as insort
+from bisect import insort
 
 def usage():
-  print("""Usage:  safe.py [-d n]
+  print("""Usage:  safe.py [-d n] [filename]
   n is maximum distance of landing to some point in the cluster, default is 10.
   
   Feed stdin with lines from the output of cluster.py, having produced
   air.tsv with the same settings as the cluster input, and lava.tsv
   with a lower-bound on Y of 0""")
 
+n=10.0
 if len(sys.argv)>1:
-  if sys.argv.pop(1)!='-d':
-    usage()
-    exit(1)
-  n=float(sys.argv.pop(1))
+  if sys.argv[1]=='-d':
+    sys.argv.pop()
+    n=float(sys.argv.pop(1))
+
+if len(sys.argv)>1:
+  infile=open(sys.argv.pop(1))
 else:
-  n=10.0
+  infile=sys.stdin
 
 class Block:
   '''Shared by Air and Lava,
@@ -42,7 +45,6 @@
       except KeyError:
         tc[k]=[y]
     # convert to lists of intervals
-    # Simplest case first
     for k,yy in tc.items():
       tyy=[yy]
       ii=[]
@@ -60,7 +62,7 @@
             break
         if clean:
           break
-      self.columns[k]=ii
+      self.columns[k]=set(ii) # so we can merge later
 
   def readPoints(self,file):
     file.readline()
@@ -88,18 +90,32 @@
   ka=[(a[0],a[2]) for a in A.points if d(a,p)<=n]
   return [(k,A.columns[k],L.columns[k]) for k in ka if k in L.columns]
 
-readHeaders(sys.modules['__main__'],sys.stdin,False)
-for l in sys.stdin:
+readHeaders(sys.modules['__main__'],infile,False)
+for l in infile:
   c=eval(l)
   ss=[]
   hits={}
   misses=[]
   for p in c:
-    s=safety(p)
-    if s:
-      pass
+    ss=safety(p)
+    if ss:
+      for (k,a,l) in ss:
+        try:
+          (aa,ll)=hits[k]
+          aa.update(a)
+          ll.update(l)
+        except KeyError:
+          hits[k]=(a,l)
     else:
       misses.append(p)
   print(c)
-  print(' %s nearby landing zones'%(
-    (lambda nm,nc:'No' if nm==nc else nc-nm)(len(misses),len(c))))
+  if hits:
+    print(' %s nearby landing columns'%len(hits))
+    for k in sorted(hits.keys(),key=lambda k:k[0]):
+      aa,ll=hits[k]
+      print("%s: %s %s"%(k,sorted(list(aa)),sorted(list(ll))))
+  else:
+    print(' No nearby landing zones')
+
+if infile!=sys.stdin:
+  infile.close()