如何在python中将多行字符串拆分为多行？

Question

I have a multi-line string:

inputString = "Line 1\nLine 2\nLine 3"

I want to have an array, each element will have maximum 2 lines it it as below:

outputStringList = ["Line 1\nLine2", "Line3"]

Can i convert inputString to outputStringList in python. Any help will be appreciated.

Answer 1

you could try to find 2 lines (with lookahead inside it to avoid capturing the linefeed) or only one (to process the last, odd line). I expanded your example to show that it works for more than 3 lines (with a little "cheat": adding a newline in the end to handle all cases:

import re

s = "Line 1\nLine 2\nLine 3\nline4\nline5"
result = re.findall(r'(.+?\n.+?(?=\n)|.+)', s+"\n")

print(result)

result:

['Line 1\nLine 2', 'Line 3\nline4', 'line5']

the "add newline cheat" allows to process that properly:

    s = "Line 1\nLine 2\nLine 3\nline4\nline5\nline6"

result:

['Line 1\nLine 2', 'Line 3\nline4', 'line5\nline6']

Answer 2

Here is an alternative using the grouper itertools recipe to group any number of lines together.

Note: you can implement this recipe by hand, or you can optionally install a third-party library that implements this recipe for you, ie pip install more_itertools .

Code

from more_itertools import grouper


def group_lines(iterable, n=2):
    return ["\n".join((line for line in lines if line))
                    for lines in grouper(n, iterable.split("\n"), fillvalue="")]

Demo

s1 = "Line 1\nLine 2\nLine 3"
s2 = "Line 1\nLine 2\nLine 3\nLine4\nLine5"


group_lines(s1)
# ['Line 1\nLine 2', 'Line 3']

group_lines(s2)
# ['Line 1\nLine 2', 'Line 3\nLine4', 'Line5']

group_lines(s2, n=3)
# ['Line 1\nLine 2\nLine 3', 'Line4\nLine5']

---

Details

group_lines() splits the string into lines and then groups the lines by n via grouper .

list(grouper(2, s1.split("\n"), fillvalue=""))
[('Line 1', 'Line 2'), ('Line 3', '')]

Finally, for each group of lines, only non-emptry strings are rejoined with a newline character.

See more_itertools docs for more details on grouper .

Answer 3

I'm hoping I get your logic right - If you want a list of string, each with at most one newline delimiter, then the following code snippet will work:

# Newline-delimited string
a = "Line 1\nLine 2\nLine 3\nLine 4\nLine 5\nLine 6\nLine 7"
# Resulting list
b = []

# First split the string into "1-line-long" pieces
a = a.split("\n")

for i in range(1, len(a), 2):

    # Then join the pieces by 2's and append to the resulting list
    b.append(a[i - 1] + "\n" + a[i]) 

    # Account for the possibility of an odd-sized list
    if i == len(a) - 2: 
        b.append(a[i + 1])

print(b)

>>> ['Line 1\nLine 2', 'Line 3\nLine 4', 'Line 5\nLine 6', 'Line 7']

Although this solution isn't the fastest nor the best, it's easy to understand and it does not involve extra libraries.

Answer 4

I wanted to post the grouper recipe from the itertools docs as well, but PyToolz' partition_all is actually a bit nicer.

from toolz import partition_all

s = "Line 1\nLine 2\nLine 3\nLine 4\nLine 5"
result = ['\n'.join(tup) for tup in partition_all(2, s.splitlines())]
# ['Line 1\nLine 2', 'Line 3\nLine 4', 'Line 5']

---

Here's the grouper solution for the sake of completeness:

from itertools import zip_longest

# Recipe from the itertools docs.
def grouper(iterable, n, fillvalue=None):
    "Collect data into fixed-length chunks or blocks"
    # grouper('ABCDEFG', 3, 'x') --> ABC DEF Gxx"
    args = [iter(iterable)] * n
    return zip_longest(*args, fillvalue=fillvalue)

result = ['\n'.join((a, b)) if b else a for a, b in grouper(s, 2)]

Answer 5

Use str.splitlines() to split the full input into lines:

>>> inputString = "Line 1\nLine 2\nLine 3"
>>> outputStringList = inputString.splitlines()
>>> print(outputStringList)
['Line 1', 'Line 2', 'Line 3']

Then, join the first lines to obtain the desired result:

>>> result = ['\n'.join(outputStringList[:-1])] + outputStringList[-1:]
>>> print(result)
['Line 1\nLine 2', 'Line 3']

Bonus: write a function that do the same, for any number of desired lines:

def split_to_max_lines(inputStr, n):
    lines = inputStr.splitlines()
    # This define which element  in the list become the 2nd in the
    # final result. For n = 2, index = -1, for n = 4, index = -3, etc.
    split_index = -(n - 1)
    result = ['\n'.join(lines[:split_index])]
    result += lines[split_index:]
    return result

print(split_to_max_lines("Line 1\nLine 2\nLine 3\nline 4\nLine 5\nLine 6", 2))
print(split_to_max_lines("Line 1\nLine 2\nLine 3\nline 4\nLine 5\nLine 6", 4))
print(split_to_max_lines("Line 1\nLine 2\nLine 3\nline 4\nLine 5\nLine 6", 5))

Returns:

['Line 1\nLine 2\nLine 3\nline 4\nLine 5', 'Line 6']
['Line 1\nLine 2\nLine 3', 'line 4', 'Line 5', 'Line 6']
['Line 1\nLine 2', 'Line 3', 'line 4', 'Line 5', 'Line 6']

Answer 6

b = "a\nb\nc\nd".split("\n", 3)
c = ["\n".join(b[:-1]), b[-1]]
print c

gives

['a\nb\nc', 'd']

Answer 7

I'm not sure what you mean by "a maximum of 2 lines" and how you'd hope to achieve that. However, splitting on newlines is fairly simple.

'Line 1\nLine 2\nLine 3'.split('\n')

This will result in:

['line 1', 'line 2', 'line 3']

To get the weird allowance for "some" line splitting, you'll have to write your own logic for that.