Editing Run-length encoding (section)

==== Python implementation ====
{{hidden|headerstyle=background:#ccccff; text-align:left;
|Imports and helper functions

|<syntaxhighlight lang="python">
from itertools import repeat, compress, groupby

def ilen(iterable):
    """
    Return the number of items in iterable.

    >>> ilen(x for x in range(1000000) if x % 3 == 0)
    333334
    """
    # using zip() to wrap the input with 1-tuples which compress() reads as true values.
    return sum(compress(repeat(1), zip(iterable)))
</syntaxhighlight>
}}

<syntaxhighlight lang="python">
def rle_encode(iterable, *, length_first=True):
    """
    >>> "".join(rle_encode("AAAABBBCCDAA"))
    '4A3B2C1D2A'
    >>> "".join(rle_encode("AAAABBBCCDAA", length_first=False))
    'A4B3C2D1A2'
    """
    return (
        f"{ilen(g)}{k}" if length_first else f"{k}{ilen(g)}" # ilen(g): length of iterable g
        for k, g in groupby(iterable)
    )
</syntaxhighlight><ref name="more-itertools">{{cite web|url=https://more-itertools.readthedocs.io/en/stable/_modules/more_itertools/more.html#run_length|date=August 2024|title=more-itertools 10.4.0 documentation}}</ref>