If the string contains an odd number of characters, how to add a ( _ ) character after the last character

Question

How to add a character(_) after the last character?

def split_string(string: str) -> list:
    n = 2
    list1 = [string[i: i + n] for i in range(0, len(string), n)]
    return list1


print(split_string("123456"))  # ["12", "34", "56"]
print(split_string("ab cd ef"))  # ["ab", " c", "d ", "ef"]
print(split_string("abc"))  # ["ab", "c_"]
print(split_string(" "))  # [" _"]
print(split_string(""))  # []

Asked By: Andrey Petrus

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Source

Answer 1

Just add a character to a temporary copy, and work with that:

def split_string(string: str) -> list:
    s = string + "_"   # <----
    list1 = [s[i: i + 2] for i in range(0, len(string), 2)]
    #        ^
    return list1

Answered By: trincot

Answer 2

The itertools module provides the definition of a function grouper:

from itertools import zip_longest


def grouper(iterable, n, *, incomplete='fill', fillvalue=None):
    "Collect data into non-overlapping fixed-length chunks or blocks"
    # grouper('ABCDEFG', 3, fillvalue='x') --> ABC DEF Gxx
    # grouper('ABCDEFG', 3, incomplete='strict') --> ABC DEF ValueError
    # grouper('ABCDEFG', 3, incomplete='ignore') --> ABC DEF
    args = [iter(iterable)] * n
    if incomplete == 'fill':
        return zip_longest(*args, fillvalue=fillvalue)
    if incomplete == 'strict':
        return zip(*args, strict=True)
    if incomplete == 'ignore':
        return zip(*args)
    else:
        raise ValueError('Expected fill, strict, or ignore')

Your function is a special case: you split your string into groups of 2, padding incomplete chunks with "_", and joining the resulting 2-tuples back into a single string.

def split_string(s):
    return list(map(''.join, grouper(s, 2, fillvalue="_")))
    # return [''.join(t) for t in grouper(s, 2, fillvalue="_")]

Answered By: chepner

Answer 3

You could just adjust the last element before you return the list:

   if len(string) % 2:
        list1[-1] += "_"

Or to support other values of n:

    if add := -len(string) % n:
        list1[-1] += "_" * add

Alternatively, with an iterator:

def split_string(string: str) -> list:
    it = iter(string)
    return [c + next(it, "_") for c in it]

Answered By: Kelly Bundy

If the string contains an odd number of characters, how to add a ( _ ) character after the last character

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