# Back propagation neural network

This is the first time I tried to write a back propagation ANN and I would like to know what more experienced people think of it. The code is meant to distinguish if text is written in English, French or Dutch.

I know my training set isn't very diverse but I just got the data from about 30 different texts, each containing 250 words in one of the 3 languages, so that's not my fault. I also know there are easier ways to do that but I wanted to learn something about ANNs.

I'd be glad if any of you would be kind enough to give me his thoughts on how I did this and how I could improve it.

import math, time, random, winsound
global Usefull
LearningRate = 0.001
InWeight = [[],[],[],[],[],[]]
#Generate random InWeights
for i in range(6):
for j in range(21):
InWeight[i].append(random.uniform(0,1))
#21 Input Values
InNeuron = [0,0,0,0,0,0,0,
0,0,0,0,0,0,0,
0,0,0,0,0,0,0]
#6 Hidden Neurons
HiddenLayer = [0, 0, 0, 0, 0, 0]
#Used to calculate Delta
HiddenLayerNoSigmoid = [0, 0, 0, 0, 0, 0]
HiddenWeight = [[],[],[]]
#Generate random HiddenWeights
for i in range(3):
for j in range(6):
HiddenWeight[i].append(random.uniform(0,1))
#3 Output Neurons
OutNeuron = [0, 0, 0]
#Used to calculate Delta
OutNeuronNoSigmoid = [0, 0, 0]
#Learning Table
#Engels - Nederlands - Frans - Desired output
test = [[11, 4, 8, 1, 14, 8, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[4, 0, 6, 0, 4, 6, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[6, 0, 6, 0, 11, 8, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[23, 0, 0, 0, 13, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[18, 4, 4, 2, 14, 8, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[14, 1, 6, 0, 10, 7, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[19, 0, 2, 0, 18, 4, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[13, 1, 1, 1, 15, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[19, 3, 1, 0, 14, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 2, 0, 5, 6, 1, 1, 8, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 3, 0, 7, 1, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 1, 0, 12, 7, 8, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 4, 0, 5, 4, 4, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 5, 1, 13, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 7, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 7, 0, 13, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 3, 14, 1, 8, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 4, 0, 2, 4, 9, 4, 3, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 3, 0, 6, 0, 8, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 2, 7, 0, 1, 0, 0, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 1, 0, 2, 0, 1, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 5, 2, 2, 0, 0, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 0, 7, 0, 2, 0, 2, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 7, 1, 1, 2, 3, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 8, 0, 2, 0, 2, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 4, 0, 3, 1, 3, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 1, 5, 1, 2, 0, 0, 0, 0, 1]]

def Sigmoid(Value):
return math.tanh(Value)

def DSigmoid(Value):
return 1.0 - Value**2

def UpdateHiddenNode():
global InNeuron, InWeight
for i in range(6):
e = 0
for j in range(21):
e += InWeight[i][j]*InNeuron[j]
HiddenLayerNoSigmoid = e
HiddenLayer[i] = Sigmoid(e)

def UpdateOutNeuron():
global HiddenLayer, HiddenWeight
for i in range(3):
e = 0
for j in range(3):
e += HiddenWeight[i][j]*HiddenLayer[j]
OutNeuron[i] = Sigmoid(e)

def UpdateDelta():
global Delta3, Delta4, Delta5, Delta6, Delta7, Delta8
Delta3 = Delta0*HiddenWeight[0][0]+Delta1*HiddenWeight[1][0]+Delta2*HiddenWeight[2][0]
Delta4 = Delta0*HiddenWeight[0][1]+Delta1*HiddenWeight[1][1]+Delta2*HiddenWeight[2][1]
Delta5 = Delta0*HiddenWeight[0][2]+Delta1*HiddenWeight[1][2]+Delta2*HiddenWeight[2][2]
Delta6 = Delta0*HiddenWeight[0][3]+Delta1*HiddenWeight[1][3]+Delta2*HiddenWeight[2][3]
Delta7 = Delta0*HiddenWeight[0][4]+Delta1*HiddenWeight[1][4]+Delta2*HiddenWeight[2][4]
Delta8 = Delta0*HiddenWeight[0][5]+Delta1*HiddenWeight[1][5]+Delta2*HiddenWeight[2][5]

def UpdateInWeights():
global Delta3, Delta4, Delta5, Delta6, Delta7, Delta8
for i in range(21):
InWeight[0][i] += LearningRate*Delta3*DSigmoid(HiddenLayerNoSigmoid[0])*InNeuron[i]
InWeight[1][i] += LearningRate*Delta4*DSigmoid(HiddenLayerNoSigmoid[1])*InNeuron[i]
InWeight[2][i] += LearningRate*Delta5*DSigmoid(HiddenLayerNoSigmoid[2])*InNeuron[i]
InWeight[3][i] += LearningRate*Delta6*DSigmoid(HiddenLayerNoSigmoid[3])*InNeuron[i]
InWeight[4][i] += LearningRate*Delta7*DSigmoid(HiddenLayerNoSigmoid[4])*InNeuron[i]
InWeight[5][i] += LearningRate*Delta8*DSigmoid(HiddenLayerNoSigmoid[5])*InNeuron[i]

def UpdateHiddenWeights():
global Delta0, Delta1, Delta2
for i in range(3):
HiddenWeight[0][i] += LearningRate*Delta0*DSigmoid(OutNeuronNoSigmoid[0])*HiddenLayer[i]
HiddenWeight[1][i] += LearningRate*Delta1*DSigmoid(OutNeuronNoSigmoid[1])*HiddenLayer[i]
HiddenWeight[2][i] += LearningRate*Delta2*DSigmoid(OutNeuronNoSigmoid[2])*HiddenLayer[i]

print("Learning...")
#Start playing Learning.wav if available, else play windows default sound
#ASYNC ensures the program keeps running while playing the sound
winsound.PlaySound("Learning.wav", winsound.SND_ASYNC)
#Start timer
StartTime = time.clock()
Iterations = 0
#Main loop
while Iterations <= 100000:
for i in range(len(test)):
for j in range(21):
InNeuron[j] = test[i][j]
UpdateHiddenNode()
UpdateOutNeuron()
Delta0 = test[i][21] - OutNeuron[0]
Delta1 = test[i][22] - OutNeuron[1]
Delta2 = test[i][23] - OutNeuron[2]
UpdateDelta()
UpdateInWeights()
UpdateHiddenWeights()
if Iterations % 1000 == 0:
PercentComplete = Iterations / 1000
print("Learning " + str(PercentComplete) + "% Complete")
Iterations += 1
#Stop playing any sound
winsound.PlaySound(None, winsound.SND_ASYNC)
print(Delta0, Delta1, Delta2)
#Save brain to SaveFile
SaveFileName = input("Save brain as: ")
SaveFile = open(SaveFileName+".txt", "w")
SaveFile.write(str(InWeight))
SaveFile.write(str(HiddenWeight))
SaveFile.close()
ElapsedTime = (time.clock() - StartTime)
print(str(ElapsedTime) + "seconds")
#Start playing Ready.wav if available, else play default windows sound
#ASYNC ensures the program keeps running while playing the sound

def Input_Frequency(Document):
WantedWords = ["i", "you", "he", "are", "the", "and", "for",
"ik", "jij", "hij", "zijn", "het", "niet", "een",
"le", "tu", "il", "avez", "une", "alors", "dans"]
file = open(Document, "r")
file.close()
#Create dictionary
word_freq ={}
#Split text in words
text = str.lower(text)
word_list = str.split(text)

for word in word_list:
word_freq[word] = word_freq.get(word, 0) + 1

#Get keys
keys = word_freq.keys()

#Get frequency of usefull words
Usefull = []
for word in WantedWords:
if word in keys:
word = word_freq[word]
Usefull.append(word)
else:
Usefull.append(0)
return Usefull

def UseIt(Input):
for i in range(len(Input)):
InNeuron[i] = Input[i]
UpdateHiddenNode()
UpdateOutNeuron()
if OutNeuron[0] > 0.99:
return ("Engelse tekst")
if OutNeuron[1] > 0.99:
return ("Nederlandse tekst")
if OutNeuron[2] > 0.99:
return ("Franse tekst")
#Documents to investigate
#Error handling checks if you input a number
while True:
try:
NumberOfDocuments = int(input("Aantal te onderzoeken documenten: "))
break
except ValueError:
print("That was not a valid number.")
x = 0
while NumberOfDocuments > x:
#Error handling checks if document exists
while True:
try:
Document = str(input("Document: "))
file = open(Document, "r")
break
except IOError:
print(UseIt(Input_Frequency(Document)))
#Stop playing any sound
if x == (NumberOfDocuments - 1):
winsound.PlaySound(None, winsound.SND_ASYNC)
x += 1

• You might want to cut the soundcode from the code, I just used it to warn me when the calculation was running and when it was done so I could test. – Daquicker Nov 17 '11 at 22:06

import math, time, random, winsound
global Usefull


A global statement outside of a function has no effect

LearningRate = 0.001


The python style guide recommends that global constants be in ALL_CAPS

InWeight = [[],[],[],[],[],[]]


The python style guide for local variable names is lower_case_with_underscores

#Generate random InWeights
for i in range(6):
for j in range(21):
InWeight[i].append(random.uniform(0,1))


Logic like this should always be in a function. Your main level should be restricted to defining functions/classes. Also you might want to consider looking into using numpy. With it you can do the above as InWeight = numpy.random.random(6, 21)

#21 Input Values
InNeuron = [0,0,0,0,0,0,0,
0,0,0,0,0,0,0,
0,0,0,0,0,0,0]


You can use InNeuron = [0] * 21. Speaking of this, the numbers 21 and 6 are showing up in multiple places. You should make them a global constant so you can change them from one place.

#6 Hidden Neurons
HiddenLayer = [0, 0, 0, 0, 0, 0]
#Used to calculate Delta
HiddenLayerNoSigmoid = [0, 0, 0, 0, 0, 0]
HiddenWeight = [[],[],[]]
#Generate random HiddenWeights
for i in range(3):
for j in range(6):
HiddenWeight[i].append(random.uniform(0,1))
#3 Output Neurons
OutNeuron = [0, 0, 0]
#Used to calculate Delta
OutNeuronNoSigmoid = [0, 0, 0]


As before, no need to type out the entire table of zeros.

#Learning Table
#Engels - Nederlands - Frans - Desired output
test = [[11, 4, 8, 1, 14, 8, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[4, 0, 6, 0, 4, 6, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[6, 0, 6, 0, 11, 8, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[23, 0, 0, 0, 13, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[18, 4, 4, 2, 14, 8, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[14, 1, 6, 0, 10, 7, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[19, 0, 2, 0, 18, 4, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[13, 1, 1, 1, 15, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[19, 3, 1, 0, 14, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 2, 0, 5, 6, 1, 1, 8, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 3, 0, 7, 1, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 1, 0, 12, 7, 8, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 4, 0, 5, 4, 4, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 5, 1, 13, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 7, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 7, 0, 13, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 3, 14, 1, 8, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 4, 0, 2, 4, 9, 4, 3, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 3, 0, 6, 0, 8, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 2, 7, 0, 1, 0, 0, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 1, 0, 2, 0, 1, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 5, 2, 2, 0, 0, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 0, 7, 0, 2, 0, 2, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 7, 1, 1, 2, 3, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 8, 0, 2, 0, 2, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 4, 0, 3, 1, 3, 0, 0, 1]]
test += [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 1, 5, 1, 2, 0, 0, 0, 0, 1]]


Why do you use += many time instead of simply creating the list in one go? For this much data I'd also probably store it in an external file.

def Sigmoid(Value):
return math.tanh(Value)

def DSigmoid(Value):
return 1.0 - Value**2


The python style guide recommends lowercase_with_underscores for function names and the variables in them.

def UpdateHiddenNode():
global InNeuron, InWeight


Avoid global variables. Stuff like this should really be in a class where InNeuron and InWeight would be attributes.

    for i in range(6):
e = 0


e is a cryptic variable name, considering expanding it

        for j in range(21):
e += InWeight[i][j]*InNeuron[j]
HiddenLayerNoSigmoid = e
HiddenLayer[i] = Sigmoid(e)


This entire function would probably be one line of code if you were using numpy. It would also run faster.

def UpdateOutNeuron():
global HiddenLayer, HiddenWeight
for i in range(3):
e = 0
for j in range(3):
e += HiddenWeight[i][j]*HiddenLayer[j]
OutNeuron[i] = Sigmoid(e)


These last two function seem to be doing basically the same thing. Can you combine them?

def UpdateDelta():
global Delta3, Delta4, Delta5, Delta6, Delta7, Delta8
Delta3 = Delta0*HiddenWeight[0][0]+Delta1*HiddenWeight[1][0]+Delta2*HiddenWeight[2][0]
Delta4 = Delta0*HiddenWeight[0][1]+Delta1*HiddenWeight[1][1]+Delta2*HiddenWeight[2][1]
Delta5 = Delta0*HiddenWeight[0][2]+Delta1*HiddenWeight[1][2]+Delta2*HiddenWeight[2][2]
Delta6 = Delta0*HiddenWeight[0][3]+Delta1*HiddenWeight[1][3]+Delta2*HiddenWeight[2][3]
Delta7 = Delta0*HiddenWeight[0][4]+Delta1*HiddenWeight[1][4]+Delta2*HiddenWeight[2][4]
Delta8 = Delta0*HiddenWeight[0][5]+Delta1*HiddenWeight[1][5]+Delta2*HiddenWeight[2][5]


Surely all that repeating code looks ugly to you.Surely all that repeating code looks ugly to you.Surely all that repeating code looks ugly to you.Surely all that repeating code looks ugly to you.Surely all that repeating code looks ugly to you.Surely all that repeating code looks ugly to you.Surely all that repeating code looks ugly to you.Surely all that repeating code looks ugly to you.Surely all that repeating code looks ugly to you.

If you make Delta a list instead of a collection of variables it should be easy to write a loop to handle it. In general, if you ever find yourself creating multiple variables differing only by a number, you should have a list or an array.

def UpdateInWeights():
global Delta3, Delta4, Delta5, Delta6, Delta7, Delta8
for i in range(21):
InWeight[0][i] += LearningRate*Delta3*DSigmoid(HiddenLayerNoSigmoid[0])*InNeuron[i]
InWeight[1][i] += LearningRate*Delta4*DSigmoid(HiddenLayerNoSigmoid[1])*InNeuron[i]
InWeight[2][i] += LearningRate*Delta5*DSigmoid(HiddenLayerNoSigmoid[2])*InNeuron[i]
InWeight[3][i] += LearningRate*Delta6*DSigmoid(HiddenLayerNoSigmoid[3])*InNeuron[i]
InWeight[4][i] += LearningRate*Delta7*DSigmoid(HiddenLayerNoSigmoid[4])*InNeuron[i]
InWeight[5][i] += LearningRate*Delta8*DSigmoid(HiddenLayerNoSigmoid[5])*InNeuron[i]


And again, you aren't lazy enough. You should be too lazy to repeat this much code. Rewrite this as a loop.

def UpdateHiddenWeights():
global Delta0, Delta1, Delta2
for i in range(3):
HiddenWeight[0][i] += LearningRate*Delta0*DSigmoid(OutNeuronNoSigmoid[0])*HiddenLayer[i]
HiddenWeight[1][i] += LearningRate*Delta1*DSigmoid(OutNeuronNoSigmoid[1])*HiddenLayer[i]
HiddenWeight[2][i] += LearningRate*Delta2*DSigmoid(OutNeuronNoSigmoid[2])*HiddenLayer[i]


Be lazy. Don't repeat yourself.

print("Learning...")
#Start playing Learning.wav if available, else play windows default sound
#ASYNC ensures the program keeps running while playing the sound
winsound.PlaySound("Learning.wav", winsound.SND_ASYNC)
#Start timer
StartTime = time.clock()
Iterations = 0
#Main loop
while Iterations <= 100000:


Use a for loop

    for i in range(len(test)):
for j in range(21):
InNeuron[j] = test[i][j]


Given that test[i] is a list, you could just say InNeuron = test[i]

        UpdateHiddenNode()
UpdateOutNeuron()
Delta0 = test[i][21] - OutNeuron[0]
Delta1 = test[i][22] - OutNeuron[1]
Delta2 = test[i][23] - OutNeuron[2]


:(

        UpdateDelta()
UpdateInWeights()
UpdateHiddenWeights()
if Iterations % 1000 == 0:
PercentComplete = Iterations / 1000
print("Learning " + str(PercentComplete) + "% Complete")


Print automatically stringify's things. You shouldn't need to call str here

    Iterations += 1
#Stop playing any sound
winsound.PlaySound(None, winsound.SND_ASYNC)
print(Delta0, Delta1, Delta2)
#Save brain to SaveFile
SaveFileName = input("Save brain as: ")
SaveFile = open(SaveFileName+".txt", "w")
SaveFile.write(str(InWeight))
SaveFile.write(str(HiddenWeight))
SaveFile.close()
ElapsedTime = (time.clock() - StartTime)


Usually I'd avoid recording time for user input here by stopping the time before the call to input above.

print(str(ElapsedTime) + "seconds")
#Start playing Ready.wav if available, else play default windows sound
#ASYNC ensures the program keeps running while playing the sound

def Input_Frequency(Document):
WantedWords = ["i", "you", "he", "are", "the", "and", "for",
"ik", "jij", "hij", "zijn", "het", "niet", "een",
"le", "tu", "il", "avez", "une", "alors", "dans"]


Constant stuff like this should really be at the main level not in a function

    file = open(Document, "r")


Why gaping the whole in read( ) It looks like you left the door open.

    file.close()
#Create dictionary
word_freq ={}


Put a space before the {} to give it a nice balance

    #Split text in words
text = str.lower(text)
word_list = str.split(text)

for word in word_list:
word_freq[word] = word_freq.get(word, 0) + 1


There is a class, collections.Counter, which makes counting stuff like this easier.

    #Get keys
keys = word_freq.keys()


No real reason to do this, just use key in word_freq instead of key in keys

    #Get frequency of usefull words
Usefull = []
for word in WantedWords:
if word in keys:
word = word_freq[word]
Usefull.append(word)
else:
Usefull.append(0)


This would be shorter to say Usefull.append(word_freq.get(word, 0)) instead of that if

    return Usefull

def UseIt(Input):
for i in range(len(Input)):
InNeuron[i] = Input[i]
UpdateHiddenNode()
UpdateOutNeuron()
if OutNeuron[0] > 0.99:
return ("Engelse tekst")
if OutNeuron[1] > 0.99:
return ("Nederlandse tekst")
if OutNeuron[2] > 0.99:
return ("Franse tekst")
#Documents to investigate
#Error handling checks if you input a number
while True:
try:
NumberOfDocuments = int(input("Aantal te onderzoeken documenten: "))
break


Stylistically, I'd put the break in an else instead of here.

    except ValueError:
print("That was not a valid number.")
x = 0
while NumberOfDocuments > x:
#Error handling checks if document exists
while True:
try:
Document = str(input("Document: "))
file = open(Document, "r")
break
except IOError:

    x += 1