Python Hangman Game Program Error

Hello this is Gulshan Negi
Well, I am writing a program for making a hangman game in Python but it shows some error at the time of its execution, I don't know what wrong I am doing here.

Here is my source code:

Code:

import random
def select_word():
    words_in_computer_memory = ['magazine','stars','computer','python','organisation']
    word = random.choice(words_in_computer_memory)
    return word
def is_gussed(word, guessed_letter_list):
    count=0
    for letters in word:
        if letters in guessed_letter_list:
            count+=1:
    if count==len(word):
        return True
    else:
        return False
def guessed_word(word, guessed_letter_list):
    string=""
    for key in word:
        if key in guessed_letter_list:
            string+=key
        else:
            string+="_ "
    return string
def available_letters(guessed_letter_list):
 
    string=""
    count=0:
    s='abcdefghijklmnopqrstuvwxyz'
    for letter in s:
        if letter in guessed_letter_list:
            count+=1
        else:
            string+=letter
    return string
def hangman_game(word):
    length=len(word)
    print('''------------------WELCOME TO HANGMAN GAME---------------------------
                                    O  
                                   /|\
                                   / \
        ''')
    print("The word you have to guess is of ",length, "letters long.")
    chances=2*len(word)
    i=0
    guessed_letter_list=[]
    while (chances!=0):    

        if word!=guessed_word(word, guessed_letter_list):
            print("You Got", chances, "Chances.")
            print("Letters you can enter should be from these ",available_letters(guessed_letter_list))
            guess=input("ENTER A LETTER ")
            print('\n'*50)

            guessInLowerCase = guess[0].lower()    
            if guessInLowerCase  in guessed_letter_list:
                print("SORRY! YOU HAVE GUSSED THIS LETTER ALREADY! ",guessed_word(word, guessed_letter_list))
            elif guessInLowerCase not in word:
                print(" SORRY! THE LETTER IS NOT IN WORD",guessed_word(word, guessed_letter_list))
                chances-=1
            else:
                guessed_letter_list.append(guessInLowerCase)
                print("NICE YOU GUSESSED THE RIGHT LETTER! ",guessed_word(word, guessed_letter_list))
          
        elif word==guessed_word(word, guessed_letter_list):
            print("YOU WON!")
            break

    else:
        print('''
        ********************************************
   YOU LOSS!!
                                 O
                                /|\
                                / \
     ******************************************''')
        print('The word was',word,)

word = select_word()
hangman_game(word)

n above code I don't know what I am missing. Can anyone give their suggestions on this?
Thanks

 

Thanks a lot for your kind response, well error is showing in line no 9 and 21.

 

Well, there was same error with both count function i.e. count+=1: (Collon is not required here). Well I checked and took its reference from here.
Thanks