Fix file read error

scan_faces.py

@@ -54,22 +54,36 @@ lcd.message("Init scanner...")
 prevFaceCount = 0
 totalUse = 0 #in face-seconds
 
+logfile = "/home/pi/scan_faces/scan_faces.log"
+
+def tail(filepath):
+	"""
+	Thanks: https://stackoverflow.com/a/41491521
+	"""
+    with open(filepath, "rb") as f:
+        first = f.readline()      # Read the first line.
+        f.seek(-2, 2)             # Jump to the second last byte.
+        while f.read(1) != b"\n": # Until EOL is found...
+            try:
+                f.seek(-2, 1)     # ...jump back the read byte plus one more.
+            except IOError:
+                f.seek(-1, 1)
+                if f.tell() == 0:
+                    break
+        last = f.readline()       # Read last line.
+    return last
+
 # make sure log file exists
-if not os.path.exists("scan_face.log")
+if not os.path.exists(logfile):
-	with open("scan_face.log","w") as f:
+	with open(logfile,"w") as f:
 		f.write("{},{},{}".format(time.time(), 0,0))
 
 # get last line of log file and update 'total use' using that.
-with open("scan_face.log", "rb") as f:
+last = tail("")
-    first = f.readline()        # Read the first line.
+bits = last.split(",")
-    f.seek(-2, os.SEEK_END)     # Jump to the second last byte.
+totalUse = bits[2]
-    while f.read(1) != b"\n":   # Until EOL is found...
-        f.seek(-2, os.SEEK_CUR) # ...jump back the read byte plus one more.
-    last = f.readline()         # Read last line.
-    bits = last.split(",")
-    totalUse = bits[2]
 
-log = open("scan_face.log", "a")
+log = open(logfile, "a")
 
 lastFaceTime = datetime.datetime.utcnow()