Why NameError?

I can't run this> NameError: name 'karl' is not defined, showrobotdialogue, 16, , 20 What's happen please tell me thank you

my code:

VOWELS = "aeiou" import re

class Chat: def showhumandialogue(self): print ("show_human") result=karl.text+" "+bot.text print (result) return result

def show_robot_dialogue(self):
        print ("show_robot")
        result=karl.text_+" "+bot.text_
        print (result)
        return result


def connect_human(self,karl):
    self.name_human = karl.name
    print ("name_human",self.name_human)

def connect_robot(self,bot):
    self.name_robot = bot.name
    print ("name_robot",self.name_robot)

class Human: def init(self,name): self.name = name print("init",self.name)

def send(self,text):
    text_=""
    for i in text:
        if(i in VOWELS):
            text_+="0"
        else:
            text_+="1"  

    self.text = self.name+" said: "+text
    self.text_ = self.name+" said: "+text_
    print ("Human__",self.name,"said:",text)

class Robot: def init(self,name): self.name = name print("init",self.name)

def send(self,text):
    text_=""
    for i in text:
        if(i in VOWELS):
            text_+="0"
        else:
            text_+="1"  

    self.text = self.name+" said: "+text
    self.text_ = self.name+" said: "+text_
    print ("send__",self.name,"said:",self.text)