Function that replaces .txt file \n (new line) with _ (underscore)?

Question

I'm trying to write a function that takes a filename as its argument and returns a string with all \n characters replaced by the _ character.

This is what I did:

def replace_space(filename):
    wordfile = open(filename)
    text_str = wordfile.read()
    wordfile.close()
    text_str.replace("\n", "_")

replace_space("words.txt")

I also tried using " " instead of "\n":

    text_str.replace(" ", "_")

Add a `return` statement to your function. – Divyanshu Srivastava May 28 '19 at 05:46 — Divyanshu Srivastava, May 28 '19 at 05:46

score 7 · Accepted Answer · answered May 28 '19 at 05:44

7

Python, unlike languages such as Haskell and Scala, will return None if it reaches the end of a function body without an explicit return statement. Therefore, you want this:

def replace_space(filename):
    with open(filename) as wordfile:
        text_str = wordfile.read()

    return text_str.replace("\n", "_")

Note also the use of with in place of open and close; it ensures your file gets closed even if you get an exception somewhere along the way.

answered May 28 '19 at 05:44

gmds

19,325
4
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Is there a way to do this without using with? curious. – puppyonkik May 28 '19 at 05:45
1

@puppyonkik `with` is basically syntactic sugar for `try-finally`; see [this answer](https://stackoverflow.com/questions/56050594/resource-aquisition-is-initialization-in-python/56050631#56050631) of mine. – gmds May 28 '19 at 05:49
But since `text_str` is defined inside of the `with`, won't it give a NameError on return if it can't open the file because it is trying to return a variable that is not defined? – funie200 May 28 '19 at 06:29
@funie200 No, because if `open` can't open the file, then it will itself raise an exception, so you won't even get to the `return`. – gmds May 28 '19 at 06:39

Devesh Kumar Singh · Answer 2 · 2019-05-28T07:36:10.447

Some suggestions for your code

You can use with context manager to open your file which will take care of closing the file for you
You need return back the updated string.

def replace_space(filename):
    text_str = ''
    #Open the file and read the contents
    with open(filename) as wordfile:
        text_str = wordfile.read()

    #Replace and return the updated string
    return text_str.replace("\n", "_")

replace_space("file.txt")

If you don't want to use the context manager, you need to explicitly open and close the file like you were doing before

def replace_space(filename):
    text_str = ''

    #Open the file
    wordfile = open(filename)
    #Do the read and replace
    text_str = wordfile.read().replace("\n", "_")

    #Close file and return updated string
    wordfile.close()
    return text_str

replace_space("file.txt")

score 0 · Answer 3 · answered May 28 '19 at 05:44

0

def replace(filename):
    with open(filename, 'r') as file:
        text = file.read()
    text = text.replace('\n', '_')
    return text

answered May 28 '19 at 05:44

Divyanshu Srivastava

1,379
11
24

Function that replaces .txt file \n (new line) with _ (underscore)?

3 Answers3