Write a Python script to convert a list of positive integers to a comma-separated string.
[1, 2, 3, 4]
def convert_list_to_string(list): 
  string = ""
  for num in list:
    string += str(num) + ","
  return string

print(convert_list_to_string([1, 2, 3, 4]))

# Output: "1,2,3,4,"