Word Ladders

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A Python Error Occurred:

Error on line 2 of Python tag (line 3 of source):
    WORDS = set(i.lower().strip() for i in open(cs_data_root+'/courses/'+cs_course+'/'+cs_path_info[-2]+'/word_ladders/__MEDIA__/words2.short.txt'))

FileNotFoundError: [Errno 2] No such file or directory: '<DATA ROOT>/courses/spring19/EX12/word_ladders/__MEDIA__/words2.short.txt'

Music for this Problem

In this problem we will be writing a successor procedure that we can use with our search code to solve Word Ladder puzzles.

In a word ladder puzzle, you are given a start word and a goal word. You must transform the start word into the goal word by transforming one letter at a time, and all intermediate words must be valid as well. In the following example, you start with the word cold and must reach the word warm:

cold
cord
card
ward
warm

In this problem, we will implement a successor function called word_ladder_successor. As usual this function will take a state and return a list of legal successor states.

Notice, however, that states in this search space are represented by strings, e.g. "oatmeal", as opposed to the tuples we saw in Design Lab 11.

We have given you a function is_valid_word(w), which returns True if w is a valid English word, and False otherwise. You should make use of this function in your code. You may also assume that all characters are lower case letters (no spaces, no capital letters, no punctuation, etc.).

If you want to test and debug on your own machine, you can download the file words2.txt to your working directory, and paste the following code into your work file:

WORDS = set(i.lower().strip() for i in open('words2.txt'))

def is_valid_word(word):
    return word in WORDS

You may find the constants and functions in Python's string module helpful; you need to import string if you want to use it.

You should debug your code in IDLE.

Enter your code for word_ladder_successor below:

A Python Error Occurred:

Error on line 41 of question tag.
    return word in WORDS""" % WORDS

NameError: name 'WORDS' is not defined