Why is creating a new list preferred over mutating the original one?

Select one answer, then check.

• Because other parts of the program might use the list in ways that we might not remember at that moment.
  Correct. The primer says mutating a list means other parts of the program using that list "now have to be kept in mind," which is why we typically avoid mutation in favor of creating new lists.
• Because we might lose the location of the items in the list.
  Not quite. Mutating a list in place does not change where its items live; the primer's concern is about other code that still relies on the list.
• Because, historically, this has been a particular cause of attrition and debate.
  Not quite. The primer gives a concrete reason (other code relying on the list), not a historical debate.
• Because enumeration of list elements doesn't work when you mutate a list.
  Not quite. enumerate works fine on a list you are mutating; that is not the primer's reason.

Which of the following statements is true about iterating over a string in Python?

Select one answer, then check.

• Using a for loop on a string will always iterate over WORDS in the string.
  Not quite. Iterating directly over a string gives characters, not words; you get words only by iterating over the result of .split().
• The split method can only be used on strings that contain commas.
  Not quite. split works on any string; without an argument it splits on whitespace, and you can pass any character to split on, not only a comma.
• If you iterate over a string using a for loop, it will give you each character one-by-one.
  Correct. The primer says "if you iterate through a string directly, then it gives you each character one-by-one, just like if you indexed the string."
• You cannot use a for loop to iterate over strings unless you also use the split method.
  Not quite. A plain for loop over a string already works, character by character; split is only needed to iterate over chunks instead.

Which of the following is NOT true about file iteration?

Select one answer, then check.

• Several files can share the same unique path.
  Correct, this is the false statement. The primer says each file is "uniquely identified by its path": if a path is unique to a file, two different files cannot share it.
• Remember to close the files.
  Not quite, this is true. The primer stresses that "you must always remember to close files once you are done with them."
• We can iterate over lines within files.
  Not quite, this is true. The File Iteration example loops for line in grade_file.
• Files are organized into a hierarchical filesystem.
  Not quite, this is true. The primer describes folders holding other folders, "leading to a hierarchy of files and folders."