CODEWITHSUNDEEP
pythonlist
grokestray
grokestray

Reputation: 31

Reading a text file line by line and converting it into a list using only read()?

So I have a txt file that contains the following numbers:

10
5
6
2
3
4
1
9
34
22
5

There is only one number per row. I want to put all the numbers in a list and use only the read() function. readline() or readlines() is not allowed.

This is what I've tried doing (note that I have to use a function like this):

def get_list1(text):
    result=[]
    for row in text:
        result.append(row)
    return result

with open("file.txt") as f:
    n = f.read()

l=get_list1(n)
print(l)

This is the output:

['1', '0', '\n', '5', '\n', '6', '\n', '2', '\n', '3', '\n', '4', '\n', '1',
 '\n', '9', '\n', '3', '4', '\n', '2', '2', '\n', '5']

As you can see it includes the \n and splits the numbers into its digits.

I want an output of

['10','5','6','2','3','4','1','9','34','22','5']

Upvotes: 1

Views: 328

Answers (2)

Patrick Artner
Patrick Artner

Reputation: 51643

The short way to do this is

def get_list1(text):
    return text.split("\n")

with open("file.txt") as f:
    get_list1(f.read())

or you can replace the function by something like

# takes care of empty lines as well and create actual integers in a list
l = list(map(int, (w.strip() for w in f.read().split() if w.strip())))

Yours is wrong because:

def get_list1(text):
    # text is a big text with \n in it
    result=[]
    # iterates the big blob of text as single characters
    for row in text:
        result.append(row)
    return result

If you can not use any split() you can parse your file once character at time:

def get_list1(text): 
    """This function takes a text with included newlines \n, and processes it
    characterwise. Each character is added into a list of lists where the last 
    of it is always a list. A character is added to that last inner list 
    if it is not a \n. 
    If a \n is encountered, the last inner list is converted to a string
    (if not empty - to account for newlines in the input) and a new empty
    list is added for the characters of the next line. At the end the case
    of last character == \n is handled. A list of line texts is returned."""
    result=[[]]
    for character in text:
        if character == "\n":
            t = ''.join(result[-1]).strip()
            if len(t) > 0:
                # change list of characters into string
                result[-1] = int(t)
                result.append([])
            else:
                result[-1].clear()
            continue
        result[-1].append(character)

    try:
        t = ''.join(result[-1]).strip()
        if len(t) > 0:
            # change list of characters into string
            result[-1] = int(t)
        else:
            result = result[:-1] 
    except:
        result = result[:-1] 

    return result


print(get_list1("1\n11\n111\n111\n11111\n11\n"))

Output:

[1, 11, 111, 111, 11111, 11]

Upvotes: 0

ppwater
ppwater

Reputation: 2277

You can use split():

def get_list1(text):
    result=[]
    for row in text:
        result.append(row)
    return result

with open("test.txt") as f:
    n = f.read().split("\n")

l=get_list1(n)
print(l)

Or just use splitlines()

def get_list1(text):
    result=[]
    for row in text:
        result.append(row)
    return result

with open("test.txt") as f:
    n = f.read().splitlines()

l=get_list1(n)
print(l)

Upvotes: 1

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