input: Write a function to explain the difference between a list and a tuple in Python. The function should take no input and return a string describing the differences. If a list is mutable while a tuple is immutable. If a list uses square brackets while a tuple uses parentheses. If lists are used when the data should be modifiable and tuples are used when the data is fixed.
  
  assert explain_list_vs_tuple()=='The difference between a list and a tuple in Python is that a list is mutable, meaning its contents can be changed, while a tuple is immutable, meaning its contents cannot be changed. A list has square brackets around it, while a tuple has parentheses around it. Lists are used when the data needs to be changed, while tuples are used when the data is fixed and cannot be changed.'
output: def explain_list_vs_tuple():
      return 'The difference between a list and a tuple in Python is that a list is mutable, meaning its contents can be changed, while a tuple is immutable, meaning its contents cannot be changed. A list has square brackets around it, while a tuple has parentheses around it. Lists are used when the data needs to be changed, while tuples are used when the data is fixed and cannot be changed.'