Custom __str__ and __repr__ are not working

Question

I am trying to convert an output such as :

decrypt : <torfuncs.TorHop instance at 0x7f44babb8440>

into something a bit more readable, the result should be a string from array. I have defined __str__ and __repr__ but even with these I am still getting the result above. What am I doing wrong?

class TorCircuit():
    def __init__(self, sock, circid):
        self.hops = []
        self.circId = circid
        self.socket = sock
        self.tempX = 0
        self.packetSendCount = 0
        self.cookie = []

    def __str__(self, hop):    
        return 'hop #%d' %  self.hops

    def __repr__(self, hop):
        return 'hop #%d' %  self.hops

    def decrypt(self, relayCell):
        for hop in self.hops:
            print "decrypt :", str(hop)
            relayCell = hop.decrypt(relayCell)
            if relayCell[1]==0 and relayCell[2]==0:
                return relayCell
        return relayCell

What I am trying to print out is the hop currently in use for the decryption

edit TorHop

class TorHop:

    def __str__(self):    
        return 'hop #' %  self.hop

    def __repr__(self):
        return 'hop #' %  self.hop

    def __init__(self, KH, Df, Db, Kf, Kb):
        self.KH = KH
        self.Df = Df
        self.Db = Db
        self.Kf = Kf
        self.Kb = Kb

        self.fwdSha = SHA.new()
        self.fwdSha.update(Df)
        self.bwdSha = SHA.new()
        self.bwdSha.update(Db)

        ctr = Counter.new(128,initial_value=0)
        self.fwdCipher = AES.new(Kf, AES.MODE_CTR, counter=ctr)
        ctr = Counter.new(128,initial_value=0)
        self.bwdCipher = AES.new(Kb, AES.MODE_CTR, counter=ctr)
    def encrypt(self, data):
        return self.fwdCipher.encrypt(data)
    def decrypt(self, data):
        return self.bwdCipher.decrypt(data)

with this I now get:

AttributeError: TorHop instance has no attribute 'hops'

Answer 1

You seem to think that using str(hop) in the TorCircuit.decrypt() class translates to self.__str__(hop). This is not the case. It translates to hop.__str__() instead.

In other words, don't put these methods on the TorCircuit class, put them on the TorHop class instead.

When you do add them to TorHop, take into account that __str__ and __repr__ do not take arguments. Remove the hop argument; self is the TorHop instance:

def __str__(self):    
    return 'hop #%d' %  self.hop

def __repr__(self):
    return 'hop #%d' %  self.hop

I'd keep the __repr__ to something a little more useful for debugging:

def __repr__(self):
    return '<TorHop(%d)>' % self.hop

perhaps.

Next, you appear to expect the hops to be numbered. They are not. You can alter your loop to add a number before the value printed for the TorHop object, using the enumerate() function:

for i, hop in enumerate(self.hops):
    print "decrypt: hop #{} {}".format(i, hop)

This will print decrypt: hop #0, then decrypt: hop #1, etc., followed by the result of hop.__str__().