old_contents: def is_even(number):
  	if number % 2 == 0:
  		return True
  	else:
  		return False
  
  
  def is_int(x):
  	if x < 0:
  		x *= -1
  	if x % 1 > 0:
  		return False
  	else:
  		return True
  
  def digit_sum(n):
  	total = 0
  	while True:
  		total += n % 10
  		if n / 10 > 0:
  			n = n / 10
  		else:
  			return total
  
  def factorial(x):
  	if x == 1:
  		return x
  	else:
  		return x * factorial(x-1)
  
  def is_prime(x):
  	if x < 2:
  		return False
  	else:
  		for num in range(2, x):
  			if x % num == 0:
  				return False
  		return True
  
  # text[::-1] is also OK
  def reverse(text):
  	result = ""
  	for i in range(len(text)-1, -1, -1):
  		result += text[i]
  	return result
  
  
  def anti_vowel(text):
  	result = ""
  	for char in text:
  		if char.lower() not in ['a', 'e','i', 'o', 'u']:
  			result += char
  	print "anti_vowel of -%s- is -%s-" % (text, result)
  	return result
  
  anti_vowel("Hey You!")
  
  
  
  
  
  
  
  
  
  
new_contents: def is_even(number):
  	if number % 2 == 0:
  		return True
  	else:
  		return False
  
  
  def is_int(x):
  	if x < 0:
  		x *= -1
  	if x % 1 > 0:
  		return False
  	else:
  		return True
  
  def digit_sum(n):
  	total = 0
  	while True:
  		total += n % 10
  		if n / 10 > 0:
  			n = n / 10
  		else:
  			return total
  
  def factorial(x):
  	if x == 1:
  		return x
  	else:
  		return x * factorial(x-1)
  
  def is_prime(x):
  	if x < 2:
  		return False
  	else:
  		for num in range(2, x):
  			if x % num == 0:
  				return False
  		return True
  
  # text[::-1] is also OK
  def reverse(text):
  	result = ""
  	for i in range(len(text)-1, -1, -1):
  		result += text[i]
  	return result
  
  
  # remove the vowel characters in text
  def anti_vowel(text):
  	result = ""
  	for char in text:
  		if char.lower() not in ['a', 'e','i', 'o', 'u']:
  			result += char
  	print "anti_vowel of -%s- is -%s-" % (text, result)
  	return result
  
  anti_vowel("Hey You!")
  
  
  # count the item occured in a list named sequence
  def count(sequence, item):
  	number = 0
  	for element in sequence:
  		if element == item:
  			number += 1
  	return number
  
  
  # replace the word in text with same length of "*"
  def censor(text, word):
  	result = []
  	for item in text.split():
  		if item == word:
  			item = "*" * len(item)
  		result.append(item)
  	return " ".join(result)
  
  print censor("this hack is wack hack", "hack") 
  
  
  # only keep then even number
  def purify(numbers):
  	result = []
  	for num in numbers:
  		if num > 1 and num % 2 == 0:
  			result.append(num)
  	return result
  
  
  
  
  
  
  
  
subject: Add more functions