Python cannot load file

Question

I am learning Python and would be grateful for your advice on this problem.

I have written a program with some functions in it to implement a simple word search game (see code below). I was given a driver program which only works if my program has been correctly implemented. I tested all my functions with examples and they seemed to work correctly but when I run the driver program I get this error message

>>> 
Traceback (most recent call last):
  File "/Users/<name>/Documents/a3_driver.py", line 88, in <module>
    words = a3.read_words(words_file)
  File "/Users/<name>/Documents/a3.py", line 266, in read_words
    fh = open(words_file)
TypeError: invalid file: None

I believe it relates to my second last function called read_words, but I cannot seem to work out the problem. Any feedback would be extremely appreciated, I have included the code for this function below (I've also included the last function as well called read_board as this is very similar and also reads a txt file, just in case i've made the same mistake twice). Thank you in advance

the driver program for the game can be downloaded from the bottom of this page: http://spark-public.s3.amazonaws.com/programming1/a3/a3.html

The read_words function creates a words list made up of the words from a file.

def read_words(words_file):
    """ (file open for reading) -> list of str

    Return a list of all words (with newlines removed) from open file
    words_file.

    # A simple .txt file used in this function simply contains the 4 words below, each printed on a new line 
    CRUNCHY
    COWS
    EAT
    GRASS

    >>> read_words('wordlist1.txt')
    ['CRUNCHY', 'COWS', 'EAT', 'GRASS']

    Precondition: Each line of the file contains a word in uppercase characters
    from the standard English alphabet.
    """

    fh = open(words_file)

    lst = []

    for line in fh:
        line = line.strip()
        for i in line.split():
            lst.append(i)

    return lst
    #print (lst)

    fh.close()

The read_board function creates a board made up of the rows of letters from a file.

def read_board(board_file):
    """ (txt file) -> list of list of str

    # A simple txt file used in this example contains the following...
    EFJAJCOWSS
    SDGKSRFDFF
    ASRJDUSKLK
    HEANDNDJWA
    ANSDNCNEOP
    PMSNFHHEJE
    JEPQLYNXDL

    >>> read_board('board1.txt')
    [['EFJAJCOWSS'], ['SDGKSRFDFF'], ['ASRJDUSKLK'], ['HEANDNDJWA'], ['ANSDNCNEOP'], ['PMSNFHHEJE'], ['JEPQLYNXDL']]


    Return a board read from open file board_file. The board file will contain
    one row of the board per line. Newlines are not included in the board.
    """

    data = []

    fh = open(board_file)

    for line in fh:
        items = line.rstrip('\r\n').split('\t')   # strip new-line characters and split     on column delimiter
        data.append(items)

    return data

    fh.close()

Do you really need to provide all this code in order to ask your question? Isolate the problem next time and you'll be more likely to get useful answers. For today: Clearly, words_file is null (None). — alexis
– alexis, Commented Dec 30, 2014 at 19:25
The problem isn't with read_words(), its with words_file — dursk
– dursk, Commented Dec 30, 2014 at 19:26
as a side note, your fh.close() is after the return data, which is therefore not called. — njzk2
– njzk2, Commented Dec 30, 2014 at 19:27
@alexis I think the problem is that he didn't know the meaning of the keyword None, for a beginner that might not be so clear. — Emil Davtyan
– Emil Davtyan, Commented Dec 30, 2014 at 19:28
The error is clear. When you try to do fh = open(words_file), it complains: TypeError: invalid file: None. Ergo, words_file is None — Zenadix
– Zenadix, Commented Dec 30, 2014 at 19:34

Jon Kiparsky · Accepted Answer · 2014-12-30 19:49:15Z

1

Looking at the driver program you've linked to, I see these lines calling your read_words function:

words_file = askopenfile(mode='r', title='Select word list file')
words = a3.read_words(words_file)
words_file.close()

As others have pointed out, what askopenfile is returning is None. I suggest you experiment with this function and determine why this is. I suspect that the filename you're entering isn't where you think it is, and this is why you're not getting a file back.

Furthermore, a little research suggests that askopenfile returns a file handle, not a filename - your code assumes that you're getting a filename (and hence you're opening it), which will also be incorrect.

answered Dec 30, 2014 at 19:49

Jon Kiparsky

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Python cannot load file

The read_words function creates a words list made up of the words from a file.

The read_board function creates a board made up of the rows of letters from a file.

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The read_words function creates a words list made up of the words from a file.

The read_board function creates a board made up of the rows of letters from a file.

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