Adding lists to a new list

Question

I did not get this question right. The function read_words turns a text file with a bunch of names in new lines into a list and it works.

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.
    Precondition: Each line of the file contains a word in uppercase characters
    from the standard English alphabet.
    """
    words_list = []
    words = words_file.readlines()
    for i in range(len(words)):
        new_word = words[i]
        for char in '\n':
            new_word = new_word.replace(char,'')
            words_list.append(new_word)
    return words_list

the problem arises when I try to get a list of lists

def read_board(board_file):
    """ (file open for reading) -> list of list of str
    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.
    """
    board_list = []
    row_list = []
    rows = read_words(board_file)
    for i in range(len(rows)):
        for  char in rows[i]:
            row_list.append(char)
        board_list.append(row_list)
    return board_list

the goal is to turn a text file of the type:

ABCD
EFGH

into [['A','B','C','D'],['E','F','G','H']]

I have already tried playing around with the indices for board_list.append(row_list) call without luck. How can I get this to work?

[list(line) for line in file]?

poke
– poke

2018-03-04 22:02:23 +00:00
Commented Mar 4, 2018 at 22:02 — poke
– poke, Commented Mar 4, 2018 at 22:02

Stephen Rauch · Accepted Answer · 2018-03-04 22:14:16Z

3

You can do that with a list comprehension and .strip() like:

Code:

def read_board(board_file):
    return [list(line.strip()) for line in read_words(board_file)]

Test Code:

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.
    Precondition: Each line of the file contains a word in uppercase characters
    from the standard English alphabet.
    """
    return [word.strip() for word in words_file.readlines()]

def read_board(board_file):
    """ (file open for reading) -> list of list of str
    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.
    """
    return [list(line) for line in read_words(board_file)]

with open('file1', 'rU') as f:
    board = read_board(f)

print(board)

Results:

[['A', 'B', 'C', 'D'], ['E', 'F', 'G', 'H']]

edited Mar 4, 2018 at 22:14

answered Mar 4, 2018 at 22:05

Stephen Rauch♦

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3 Comments

G_M Over a year ago

If you strip the lines in read_words, why do you strip them again in read_board?

Guriqbal Chouhan Over a year ago

its... beautiful. Also i didn't know you could call return and for loop in the same line. I'm a changed man.

Stephen Rauch Over a year ago

@GuriqbalChouhan List comprehension will definitely change the way you look at code.

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