Python 将文件读入二维列表 - newline=None vs strip(“\r\n”)

Question

EDIT: bigbounty asked for sample data. I'm not sure how to keep the newlines when pasting here, so I've provided an image instead. See below.

I'm trying to determine the correct and most Pythonic way to strip newlines when reading data from an eternal file into a 2d list. I'm having trouble working out what newline does within open() (and yes, I have checked the docs - it still hasn't clicked for me). Is the code below the correct way to read data into a 2d list, avoiding capturing new line characters? Is any part of it redundant (eg newline=None ?)

EDIT: I'm on windows, but looking for a cross-platform solution.

with open(file_name, "r", newline=None) as fh:
    list_2d = [[char for char in line.strip("\r\n")] for line in fh]

Answer 1

If you want to be compatible with all platforms, you can open w.r.t. 'rU' mode which opens your file in Universal newline mode and then every newline occurrence will appear as a '\n' character (so then you only need to count '\n' chars). Since Python 3, it is deprecated , the 'rU' mode equals to newline=None , meaning that the code snippet is cross-platformatic.

list_2d = []
with open(file_name, newline=None) as fh:
     list_2d.append([x for x in line.split("\n")])

No need to use 'r' specifier if you just wish to read because it is default argument already.

Answer 2

If you don't mind reading the whole file into memory in one go (which, it seems, you don't mind doing, since you're consuming the entire file and stuffing it into a list), you could use lines = file.read().splitlines() , which would be a list of strings, where each string is one line (with no trailing carriage return or newline characters).

Answer 3

Just don't put \n char in the list.

with open('a.txt', "r") as fh:
    list_2d = [[char for char in line if char!='\n'] for line in fh]

Answer 4

You don't need to mention.

1. Read-only mode, that's default.
2. newLine = None, that's default.

with open(file_name) as fh:
    list_2d = [[char for char in line if char != "\n"] for line in fh]

Answer 5

The newline argument to open enables universal newline mode if it is None or '' . The difference between these two is that None also translates the newline characters to \n when the file is read (and translates them back if the file is written), whilst '' doesn't perform this translation.

So if you use open with newline=None , you can expect any line ending in the file to be returned to you as \n , whichever platform you are on.

Since newline=None is the default (similarly, read for text mode is the default) your example can be written for any platform as:

with open(file_name) as fh:
    list_2d = [[char for char in line.strip("\n")] for line in fh]