Two small changes:

1. Fixed bug where boolean "and" was incorrectly used instead of bitwise "&".  We're testing a bit in a byte.
2. Moved the sleep call to BEFORE the first read.  Occasional errors with immediate read after write.

Author: codesimian

Adafruit_VCNL4000/Adafruit_VCNL4000.py

@@ -46,16 +46,16 @@ def __init__(self, address=0x13):
   def read_proximity(self):
     self.i2c.write8(VCNL4000_COMMAND, VCNL4000_MEASUREPROXIMITY)
     while True:
+      time.sleep(0.001)
       result = self.i2c.readU8(VCNL4000_COMMAND)
-      if (result and VCNL4000_PROXIMITYREADY):
+      if (result & VCNL4000_PROXIMITYREADY):
         return self.i2c.readU16(VCNL4000_PROXIMITYDATA)
-      time.sleep(0.001)
 
   # Read data from ambient sensor  
   def read_ambient(self):
     self.i2c.write8(VCNL4000_COMMAND, VCNL4000_MEASUREAMBIENT)
     while True:
+      time.sleep(0.001)
       result = self.i2c.readU8(VCNL4000_COMMAND)
-      if (result and VCNL4000_AMBIENTREADY):
+      if (result & VCNL4000_AMBIENTREADY):
         return self.i2c.readU16(VCNL4000_AMBIENTDATA)
-      time.sleep(0.001)