Crossword Solving Companion

Question

I am writing a program that takes letters and indexes and spits out crossword answers (not a crossword solver, but a tool to aid in solving crosswords, if that makes sense).

I've written two versions of the algorithm, but neither seems to work correctly. The first one I tried was this:

fin = open('words.txt')

def answer_finder():
    global fin
    possible_answers = []
    length = int(raw_input("How long is the word?"))
    letter_1 = raw_input("What is the first letter that you know?").lower
    letter_1_index = int(raw_input("How many letters into the word is that letter?")) - 1
    letter_2 = raw_input("What is the second letter that you know?").lower
    letter_2_index = int(raw_input("How many letters into the word is that letter?")) - 1
    letter_3 = raw_input("What is the third letter that you know?").lower
    letter_3_index = int(raw_input("How many letters into the word is that letter?")) - 1
    for i in fin:
        if len(i) == length:
            if i[letter_1_index] == letter_1 and i[letter_2_index] == letter_2 and i[letter_3_index] == letter_3:
                possible_answers.append(i)
    return possible_answers

I realize it's kinda ugly, but this was more of a proof of concept for the algorithm. The user input will be changed later. Anyway, this seems to return an empty list no matter what I try.

The second version was essentially the same, but relied on nested if statements instead of boolean operators:

def answer_finder():
    global fin
    possible_answers = []
    length = int(raw_input("How long is the word?"))
    letter_1 = raw_input("What is the first letter that you know?").lower
    letter_1_index = int(raw_input("How many letters into the word is that letter?")) - 1
    letter_2 = raw_input("What is the second letter that you know?").lower
    letter_2_index = int(raw_input("How many letters into the word is that letter?")) - 1
    letter_3 = raw_input("What is the third letter that you know?").lower
    letter_3_index = int(raw_input("How many letters into the word is that letter?")) - 1
    for i in fin:
        if len(i) == length:
            if i[letter_1_index] == letter_1:
                if i[letter_2_index] == letter_2:
                    if i[letter_3_index] == letter_3:
                        possible_answers.append(i)
    return possible_answers

This, too, returns an empty list. The list of words I am using comes from here. I'm assuming I am missing something obvious, since I'm new to working with external files. I should point out that these functions are prototypes of the former, and both work just fine:

def greater_than_20():
    global fin
    li = []
    for i in fin:
        if len(i) > 20:
            li.append(i)
    return li

def first_letter_length_finder():
    global fin
    length = int(raw_input("How long is the word?"))
    first_letter = raw_input("What is the first letter?")
    li = []
    for i in fin:
        if len(i) == length and i[0] == first_letter:
            li.append(i)
    print li
    return li

EDIT: Just for reference, here is the code in its entirety (including commented-out sections of code.)

fin = open('words.txt')
print fin

def greater_than_20():
    global fin
    li = []
    for i in fin:
        if len(i) > 20:
            li.append(i)
    return li

def first_letter_length_finder():
    global fin
    length = int(raw_input("How long is the word?"))
    first_letter = raw_input("What is the first letter?")
    li = []
    for i in fin:
        if len(i) == length and i[0] == first_letter:
            li.append(i)
    print li
    return li

def answer_finder():
    global fin
    possible_answers = []
    length = int(raw_input("How long is the word?"))
    letter_1 = raw_input("What is the first letter that you know?").lower
    letter_1_index = int(raw_input("How many letters into the word is that letter?")) - 1
    letter_2 = raw_input("What is the second letter that you know?").lower
    letter_2_index = int(raw_input("How many letters into the word is that letter?")) - 1
    letter_3 = raw_input("What is the third letter that you know?").lower
    letter_3_index = int(raw_input("How many letters into the word is that letter?")) - 1
    for i in fin:
        if len(i) == length:
#            if i[letter_1_index] == letter_1 and i[letter_2_index] == letter_2 and i[letter_3_index] == letter_3:
#                possible_answers.append(i)
            if i[letter_1_index] == letter_1:
                if i[letter_2_index] == letter_2:
                    if i[letter_3_index] == letter_3:
                        possible_answers.append(i)
    return possible_answers

Answer 1

You are using the string.lower method, but you missed the ().

>>> letter_3 = raw_input("What is the third letter that you know?").lower
What is the third letter that you know?a
>>> letter_3
<built-in method lower of str object at 0x104e514e0>

>>> letter_3 = raw_input("What is the third letter that you know?").lower()
What is the third letter that you know?a
>>> letter_3
'a'

Without the parentheses, you are assigning not the value of the .lower function, but the function itself.

EDIT: For the record (because I can't leave comments), your method of using for i in fin is fine, since files are iterable, delimited by \n.

Answer 2

You need to read you data out of the file first before trying to use the data.

fin = file('words.txt').readlines ()