up vote 3 down vote favorite
1

I have to list a integers from a text file separated by newlines into a python list. I ended up with the code above which works (for my case) but certainly is far form optimal.

def readIntegers(pathToFile):

    f = open(pathToFile)
    contents = f.read()
    f.close()

    tmpStr = ""

    integers = []

    for char in contents:

        if char == '\r':
            integers.append(int(tmpStr))
            tmpStr = ""
            continue

        if char == '\n':
            continue

        tmpStr += char

    return integers

Now I have much less code, but I'm not sure for which cases split() works correctly.

def readIntegers(pathToFile):

    with open(pathToFile) as f:
        a = [int(x) for x in f.read().split()]
    return a
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2 Answers

up vote 8 down vote accepted

No need for split (you can use readlines). But no need for readlines, for that matter:

def read_integers(filename):
    with open(filename) as f:
        return map(int, f)

or, if that’s more to your fancy:

def read_integers(filename):
    with open(filename) as f:
        return [int(x) for x in f]

A file object is simply iterable in Python, and iterates over its lines.

Note that, contrary to what I said earlier, wrapping the file object in a with block is highly recommended. Python doesn’t actually guarantee (although it recommends it) that objects are disposed of automatically at the end of the scope. Worse, it’s not guaranteed that a file object that is collected actually closes the underlying stream.

(Note that I’ve adapted the method name to Python conventions.)

share|improve this answer
Thx for your answer :) I didn't think of using map here. – Nils Jun 11 '12 at 6:02
up vote 5 down vote

A bit faster version:

def readIntegers(filename):
    return map(int, open(filename).read().split())
share|improve this answer
Cool, what if I wanted to skip parsing anything that is not an integer? – Leonid Jun 10 '12 at 19:29
1  
Didn't get it - is it a new question? :) If you want to extract integers ony - use the re.findall('\d+', open(filename).read().split()) – cat_baxter Jun 10 '12 at 19:49
3  
It is not recommended that you simply open() files, without explicitly close()ing them afterwards. Adding a with clause to your answer would make it an ideal solution. – Joel Cornett Jun 10 '12 at 20:50
@Joel I’m slightly baffled. Apart from the with block remark which is true, what makes this answer better than mine in your opinion? Isn’t read().split() both unnecessary and potentially inefficient? – Konrad Rudolph Jun 12 '12 at 10:19
@KonradRudolph: I actually didn't read your solution until just now. I was merely informing cat_baxter know about the explicit closing. Now that I have read your solution, I'll +1 it. – Joel Cornett Jun 12 '12 at 17:20

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