review comments from Allyson MacDonald

code/hash_example.py

@@ -5,7 +5,14 @@ import hashlib
     
 text = "I am Satoshi Nakamoto"
 
-for nonce in xrange(20):  # iterate nonce from 0 to 19
-    input = text + str(nonce)  # add the nonce to the end of the text
-    hash = hashlib.sha256(input).hexdigest() # calculate the SHA-256 hash of the input (text+nonce)
-    print input, '=>',  hash # show the input and hash result
+# iterate nonce from 0 to 19
+for nonce in xrange(20): 
+    
+    # add the nonce to the end of the text
+    input = text + str(nonce) 
+     
+    # calculate the SHA-256 hash of the input (text+nonce)
+    hash = hashlib.sha256(input).hexdigest() 
+    
+    # show the input and hash result
+    print input, '=>',  hash 

code/proof-of-work-example.py

@@ -8,11 +8,13 @@ max_nonce = 2 ** 32 # 4 billion
 
 def proof_of_work(header, difficulty_bits):
     
+    # calculate the difficulty target
     target = 2 ** (256-difficulty_bits)
     
     for nonce in xrange(max_nonce):
         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
@@ -26,21 +28,34 @@ if __name__ == '__main__':
     
     nonce = 0
     hash_result = ''
-        
+     
+    # 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..."
+        
+        # checkpoint the current time
         start_time = time.time()
-        new_block = 'test block with transactions' + hash_result # make a new block which includes the hash from the previous block
-        (hash_result, nonce) = proof_of_work(new_block, difficulty_bits) # find a nonce for the new block
+        
+        # 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 
+        
+        # find a valid nonce for the new block
+        (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
     
         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