long(), print(), xrange() for Python 3

Also remove trailing whitespace

code/proof-of-work-example.py

@@ -4,60 +4,61 @@
 import hashlib
 import time
 
-max_nonce = 2 ** 32 # 4 billion
+try:
+    long        # Python 2
+    xrange
+except NameError:
+    long = int  # Python 3
+    xrange = range
+
+max_nonce = 2 ** 32  # 4 billion
+
 
 def proof_of_work(header, difficulty_bits):
-    
     # calculate the difficulty target
-    target = 2 ** (256-difficulty_bits)
-    
+    target = 2 ** (256 - difficulty_bits)
+
     for nonce in xrange(max_nonce):
-        hash_result = hashlib.sha256(str(header)+str(nonce)).hexdigest()
-        
+        hash_result = hashlib.sha256(str(header) + str(nonce)).hexdigest()
+
         # check if this is a valid result, below the target
         if long(hash_result, 16) < target:
-            print "Success with nonce %d" % nonce
-            print "Hash is %s" % hash_result
-            return (hash_result,nonce)
-            
-    print "Failed after %d (max_nonce) tries" % nonce
+            print("Success with nonce %d" % nonce)
+            print("Hash is %s" % hash_result)
+            return (hash_result, nonce)
+
+    print("Failed after %d (max_nonce) tries" % nonce)
     return nonce
 
-    
+
 if __name__ == '__main__':
-    
     nonce = 0
     hash_result = ''
-     
-    # difficulty from 0 to 31 bits  
+
+    # difficulty from 0 to 31 bits
     for difficulty_bits in xrange(32):
-        
         difficulty = 2 ** difficulty_bits
-        print "Difficulty: %ld (%d bits)" % (difficulty, difficulty_bits)
-    
-        print "Starting search..."
-        
+        print("Difficulty: %ld (%d bits)" % (difficulty, difficulty_bits))
+        print("Starting search...")
+
         # checkpoint the current time
         start_time = time.time()
-        
+
         # make a new block which includes the hash from the previous block
         # we fake a block of transactions - just a string
-        new_block = 'test block with transactions' + hash_result 
-        
+        new_block = 'test block with transactions' + hash_result
+
         # find a valid nonce for the new block
-        (hash_result, nonce) = proof_of_work(new_block, difficulty_bits) 
-        
+        (hash_result, nonce) = proof_of_work(new_block, difficulty_bits)
+
         # checkpoint how long it took to find a result
         end_time = time.time()
-        
+
         elapsed_time = end_time - start_time
-        print "Elapsed Time: %.4f seconds" % elapsed_time
-    
+        print("Elapsed Time: %.4f seconds" % elapsed_time)
+
         if elapsed_time > 0:
-            
+
             # estimate the hashes per second
-            hash_power = float(long(nonce)/elapsed_time)
-            print "Hashing Power: %ld hashes per second" % hash_power
-    
-    
-    
+            hash_power = float(long(nonce) / elapsed_time)
+            print("Hashing Power: %ld hashes per second" % hash_power)