Python Does anyone know why this happens?

[Average_Student]

in my computer science class we are learnign about searching through files.

I have a binary and linear searching method where they search the same document for spelling errors by comparing it to a dicitonary.
the problem is that if I try to run them back to back it wont work. they both work seperately but not one after another. I suspect it is because the file itself remembers what position you searched last because if you close and then re-open the file between function calls, it works.

her is my code if you would like to see:

import re
 
# This function takes in a line of text and returns
# a list of words in the line.
# basically just to make the formatting of the dictionary and alice in wonderland match
# also splits into lines which allow us to detect which line a word is on
def split_line(line):
    return re.findall('[A-Za-z]+(?:\'[A-Za-z]+)?',line)




# Opens the dictionary file and stores it in the variable 'file'
file = open("dictionary.txt")


dictionary_list = []
for line in file:
    # Strips the dictionary for formatting reasons
    line = line.strip()
    # Appends dicitionary to a list
    dictionary_list.append(line)
 
file.close()

# Opens the alice in wonderland file
file = open("alice_in_wonderland_200.txt")


# Function that uses the linear search method to find the spelling errors
def linear_search():
    print('- - - Linear Search - - -')
    #counter do detect what line a word is on
    line_number = 0
    # for each line in the file
    for line in file:
        # Variable we use to tell what line the spelling error is on
        line_number += 1
        # splits the lines for formatting reasons and sets it to 'words'
        for words in split_line(line):
            i = 0
            # a loop that continue until the dictionart is over or it find a spelling error
            while i < len(dictionary_list) and dictionary_list != words.upper():
                i += 1
            if not i < len(dictionary_list):
                print('line', line_number, 'has a possible misspelled word:', words)


# A binary search function that compares the words uning < > symbols to find the spelling errors faster
def binary_search():
    print('- - - Binary Search - - -')
    line_number = 0
    # for each line in the file
    for line in file:
        line_number += 1
        # splits the lines for formatting reasons and sets it to 'words'
        for words in split_line(line):
            # a key to tell the program what word its looking for
            key = words.upper()
            lower_bound = 0
            upper_bound = len(dictionary_list)-1
            found = False
            # Loop until we find the item, or our upper/lower bounds meet
            while lower_bound <= upper_bound and not found:
            
                # Find the middle position
                middle_pos = (lower_bound + upper_bound) // 2
            
                # Figure out if we:
                # move up the lower bound, or
                # move down the upper bound, or
                # we found what we are looking for
                if dictionary_list[middle_pos] < key:
                    lower_bound = middle_pos + 1
                elif dictionary_list[middle_pos] > key:
                    upper_bound = middle_pos - 1
                    
                else:
                    found = True
                    
                    
            # if it doesent find the word, aka its a spelling mistake, it prints this
            if not found:
                print('line',line_number,'has a possible misspelled word:', words)
            



# just calls the functions
linear_search()
print('\n')
# here I close and open the files because the second function wont work if I dont
file.close
file = open('alice_in_wonderland_200.txt')
binary_search()

 

[Deleted member 2829]

I suspect it is because the file itself remembers what position you searched last because if you close and then re-open the file between function calls, it works.

Yes, that surely is your problem. After your first search you are at end-of-file, and the second search falls right through without being able to read anything. Indeed, reopening the file does the trick. If you don't like that, perhaps Python has a command (like the seek() command in C) to set the file position back to zero.

 

[hanginthere]

Just a suggestion, I find it is easier to use an implicit context manager. That way you never have to worry about closing a file. For example:

for line in open('dictionary.txt'):
    dictionary_list.append(line.strip())

The file is automatically closed when the loop terminates.

Also, when you comment a function, put the comment inside as in

def split_line(line):
    """
    This function takes in a line of text and returns a list of words in the line.
    """
    return re.findall('[A-Za-z]+(?:\'[A-Za-z]+)?',line)

 

[Deleted member 2829]

However if you want to do multiple searches in one file I would choose to leave it open and use file.seek(0) before each search.