代写ADT，围绕Array-Based List进行各种变换。
Requirement
To be able to implement and use basic containers in Python.
Note
- You should provide documentation and testing for each piece of functionality in your code. Your documentation needs to include pre and post conditions, and information on any parameters used.
- Create a new file/module for each task or subtask.
- Name your files task[num]_[part] to keep them organised.
Testing
For this prac, you are required to write:
(1) a function to test each function or method you implement, and
(2) at least two test cases per function.
The cases need to show that your functions or methods can handle both valid and invalid inputs.
Task 1
Implement a complete version of an Array-Based List. Use 100 as the maximum number of elements. Include implementations for the following 10 functions:
- __str__(self): Returns a string representation of the list. Structure the string so that there is one item per line. Called by str(self)
- __len__(self): Returns the length of the list. Called by len(self)
- __contains__(self, item): Returns True if item is in the list, False otherwise. Called by item in self
- __getitem__(self, index): Returns the item at index in the list, if index is non-negative. If it is negative, it will return the last item if index is 1, the second-to last if index is 2, and so on up to minus the length of the list, which returns the first item. The function raises an IndexError if index is out of the range from -len(self) to len(self). Called by self[index]
- __setitem__(self, index, item): Sets the value at index in the list to be item. The index can be negative, behaving as described above. Raises an IndexError if index is out of the range from -len(self) to len(self). Called by self[index] = item
- __eq__(self, other): Returns True if this list is equivalent to other. Called by self == other
- append(self, item): Adds item to the end of the list. Remember the underlying array is and should remain of fixed size. The operation should raise an Exception if the list is full.
- prepend(self, item): Adds item to the beginning of the list. Remember the underlying array is and should remain of fixed size. The operation should raise an Exception if the list is full.
- insert(self, index, item): Inserts item into self before position index. The index can be negative, behaving as described above. Raises an IndexError if index is out of the range from -len(self) to len(self).
- remove(self, item): Deletes the first instance of item from the list. Raises a ValueError if item does not exist in self
- delete(self, index): Deletes the item at index from the list, moving all items after it towards the start of the list. The index can be negative, behaving as described above. Raises an IndexError if index is out of the range from -len(self) to len(self).
Task 2
Modify your list implementation so that the size of the underlying array is dynamic. The base size of the array is 50 and should never be less than 50. However, if the list becomes full, it is resized to be 2 times larger than the current size. Likewise, the underlying size should decrease by half if the underlying array is larger than the base size but the content occupies less than 14 of the available space. When resizing the list, retain the contents of the list. That is, when it is initially filled, it will be resized to 100 items, then 200, while retaining the contents initially in it. The same happens when the size of the array shrinks. Remember the underlying array is and should remain of fixed size.
Task 3
Implement a function that takes a filename as input and reads it into an instance of the class you implemented on Task 2. For each line in the file, store it as a single item in the list.
Background
The editor ed was one of the first editors written for UNIX. In this prac we will use the Array-Based list to implement a version of a line-oriented text editor based on ed. The text editor ed is very similar to the common UNIX text editors vi and vim (it is in fact their predecessor). 2
Important: Our commands will be different from the ed commands.
To implement a simple line-oriented text editor, the idea is as follows. Suppose a file contains the following lines:
Yossarian decided
not to utter
another word.
where the string “Yossarian decided” is considered to be in line 1, “not to utter” is considered to be in line 2, etc. We want to store every line in the file in a data type that allows users to easily manipulate (delete/add/print) any line by simply providing the line number they want to modify. This means we should use a list data type (as opposed to a stack or a queue).
Task 4
Write a text editor as a Python program that allows a user to perform the 6 commands shown below using a menu. It is advisable that the Editor itself is a class with an attribute containing a list of words. The list should be the type you have implemented on Task 2.
- insert num: which inserts a line of text (given by the user) in the list before position num, and raises an exception if no num is given
- read filename: which opens the file, filename, reads all the lines in from the file, put each line as a separate item into a list, and then closes the file.
- write filename: which creates or opens a file, filename, writes every item in the list into the file, and then closes the file.
- print num: which prints the line at position num, and if no num is given prints all the lines.
- delete num: which deletes the line of text in the list at position num, and deletes all the lines if no num is given.
- quit: which quits the program.
Important: All errors should be caught and a question mark, ?, should be printed when an error occurs. Negative number lines are possible and should be handled following the convention described for the original list implementation. For example, num = -1 refers to the last line of the text.
Tip: When you are testing your code, it is handy to have a source of reasonably large text files that you can use as test data. There is a huge repository of public domain text files at Project Gutenberg’s websites.
You are encouraged to download a couple of ebooks from here and use them to make sure your code can deal with large files. Be sure to download plain-text format, though - your program is not expected to deal with other formats.
Task 5
- Add a new function, search to the editor, which takes a word and prints the line numbers in which the target word appears. Search should be case insensitive. Search should work as expected in a standard text editor, for example ignoring punctuation.
- Add a new function, count to the editor, which counts the number of characters and the number of words in the text. We will ignore spaces and punctuation, and count as words anything that is not surrounded by alphabetical characters. For example,
This function must be accessible through the menu via commands search and count.
Task 6
The sequence of actions made in a text editor can be stored during execution to facilitate undoing actions. When a user chooses to undo an operation the most recent action should have its changes reversed. This indicates that a last in, first out data structure would be suitable for storing the actions.
Implement a Stack ADT of your choosing (Linked or Array-based) and use it to implement in your editor the undo feature. Add this to your menu using the command undo.