Need help with searching for strings in sublists

Dev Shed Forums Sponsor:

November 3rd, 2012, 02:37 PM

nump_teey

Registered User

Join Date: Nov 2012

Posts: 2

Time spent in forums: 44 m 59 sec
Reputation Power: 0

Need help with searching for strings in sublists

Hi, I'm new to Python and programming. I'm trying to check whether a string occurs in sublists. In this case the check isn't whether the string appears in one sublist, it is whether the string matches the letters at a specific index in the sublists. I have defined 2 functions for this, the 2nd function reuses the first:

python Code:

Original - python Code

def str_from_indices(letter_list, index_number):
    ''' (list of list of str, int) -> str
    Return string from letter_list using index_number.
    e.g.
    >>> str_from_indices([['A', 'B', 'C', 'D'], ['E', 'F', 'G', 'H']], 1)
    'BF'
    '''
 
    letters_from_index = ""
    for letter in letter_list:
        letters_from_index = letters_from_index + str(letter[index_number])
 
    return letters_from_index
 
 
def word_in_indices(letter_list, word):
    ''' (list of list of str, str) -> bool
    Return True if word appears in an index of letter_list.
    e.g.
    >>> word_in_indices([['A', 'B', 'C', 'D'], ['E', 'F', 'G', 'H']], 'NO')
    False
    >>> word_in_indices([['A', 'B', 'C', 'D'], ['E', 'F', 'G', 'H']], 'DH')
    True
    '''
 
    for index_number in range(len(letter_list)):
        if word in str_from_indices(letter_list, index_number):
            return True
        else:
            return False

I think the for loop in the 2nd function and the use of range and len is where I'm going wrong, my function is only checking indices 0 & 1 so I'm getting a return of False everytime I try to find a string in indices 2 & 3.

I'm looking for an answer ideally, although a nudge in the right direction to fixing the code would also be great!

November 3rd, 2012, 05:28 PM

b49P23TIvg

Contributing User

Join Date: Aug 2011

Posts: 3,364

Time spent in forums: 1 Month 2 Weeks 3 Days 10 h 28 m 48 sec
Reputation Power: 383

I fixed word_in_indices. Thank you immensely for providing doctests.

Code:

'''
$ python -m doctest q.py
['AE', 'BF', 'CG', 'DH']
['AE', 'BF', 'CG', 'DH']
'''

import sys

def str_from_indices(letter_list, index_number):
    ''' (list of list of str, int) -> str
    Return string from letter_list using index_number.
    e.g.
    >>> str_from_indices([['A', 'B', 'C', 'D'], ['E', 'F', 'G', 'H']], 1)
    'BF'
    '''

    letters_from_index = ""
    for letter in letter_list:
        letters_from_index = letters_from_index + str(letter[index_number])

    return letters_from_index

def word_in_indices(letter_list, word):
    ''' (list of list of str, str) -> bool
    Return True if word appears in an index of letter_list.
    e.g.
    >>> word_in_indices([['A', 'B', 'C', 'D'], ['E', 'F', 'G', 'H']], 'NO')
    False
    >>> word_in_indices([['A', 'B', 'C', 'D'], ['E', 'F', 'G', 'H']], 'DH')
    True
    '''

    # Assume the lists in letter_list have equal length.
    # Form all the words.
    words = []
    for i in range(len(letter_list[0])):
        words.append(str_from_indices(letter_list,i))

    # debugging, display all the words to stderr.
    # This way doctest passes.
    sys.stderr.write(str(words)+'\n')

    # decide if the word appears, and return the result
    return word in words

__________________
[code]Code tags[/code] are essential for python code!

November 3rd, 2012, 06:52 PM