I took this gist https://gist.github.com/benallard/8042835 and modified it a little so it worked for my needs. (mainly encoding issues and bigger file chunks)

xml_split.py

#!/usr/bin/env python

#based off this gist https://gist.github.com/benallard/8042835
#modified it a little so it worked for my needs. (mainly encoding issues and bigger file chunks)

import os
import xml.parsers.expat
from xml.sax.saxutils import escape
from optparse import OptionParser
from math import log10


# How much data we process at a time
CHUNK_SIZE = 1024 * 1024

# The sequence of element leading us to the current one
path = []

# How far we are in the current file
cur_size = 0
# From how much should we start another file
MAX_SIZE = (1024*1024)*3 # 1Mb * n (in this case 3Mb)

# The current index
cur_idx = 0
# The current file handle we are writing to
cur_file = None

# The format string used to introduce the index in the file to be written
FMT = ".%d"

# The filename we are playing with
out_dir = None
root = None
ext = None

# The xml declaration of the file.
xml_declaration = None

# What was the signature of the last start element
start = None

# if we are currently in the process of changing file
ending = False

def attrs_s(attrs):
    """ This generate the XML attributes from an element attribute list """
    l = ['']
    for i in range(0,len(attrs), 2):
        l.append('%s="%s"' % (attrs[i], escape(attrs[i+1])))
    return ' '.join(l)

def next_file():
    """ This makes the decision to cut the current file and starta new one """
    global cur_size, ending
    if (not ending) and (cur_size > MAX_SIZE):
        # size above threshold, and not already ending
        global cur_file, cur_idx
        print("part %d Done" % cur_idx)
        ending = True
        # Close the current elements
        for elem in reversed(path):
            end_element(elem[0])
        # Close the file
        cur_file.close()
        # reset the size
        cur_size = 0
        # Open another file
        cur_idx += 1
        cur_file = open(os.path.join(out_dir, root + FMT % cur_idx + ext),
                        'wt',encoding='utf8')
        if xml_declaration is not None:
            cur_file.write('<?xml%s?>\n' % attrs_s(xml_declaration))
        # Start again where we stopped
        for elem in path:
            start_element(*elem)
        # We are done 'ending'
        ending = False


def xml_decl(version, encoding, standalone):
    global xml_declaration
    l = ['version', version, 'encoding', encoding]
    if standalone != -1:
        l.extend(['standalone', 'yes' if standalone else 'no'])
    xml_declaration = l
    cur_file.write('<?xml%s?>\n' % attrs_s(xml_declaration))


def start_element(name, attrs):
    """ Called by the parser when he meet a start element """
    global cur_size, start
    if start is not None:
        # Chaining starts after each others
        cur_file.write('<%s%s>' % (start[0], attrs_s(start[1])))
    start = (name, attrs)
    if ending:
        return
    cur_size += len(name) + sum(len(k) for k in attrs)
    path.append((name, attrs))


def end_element(name):
    """ Caled by the parser when he meet an end element """
    global cur_size
    global start
    if start is not None:
        # Empty element, good, we did not wrote the start part
        cur_file.write('<%s%s/>' % (start[0],attrs_s(start[1])))
    else:
        # There was some data, close it normaly
        cur_file.write('</%s>' % name)
    start = None
    if ending:
        return
    elem = path.pop()
    assert elem[0] == name
    cur_size += len(name)
    next_file()


def char_data(data):
    """ Called by the parser when he meet data """
    global cur_size, start
    wroteStart = False
    if start is not None:
        # The data belong to an element, we should write the start part first
        cur_file.write('<%s%s>' % (start[0], attrs_s(start[1])))
        start = None
        wroteStart = True
    # ``escape`` is too much for us, only & and < ned to be escaped there ...
    data = data.replace('&', '&amp;')
    data = data.replace('<', '&lt;')
    if data == '>':
        data = '&gt;'
    cur_file.write(data)
    cur_size += len(data)
    if not wroteStart:
        # The data was outside of an element, it could be the right moment to
        # make the split
        next_file()

def main(filename, output_dir):
    # Create a parser
    p = xml.parsers.expat.ParserCreate()
    # We want to reproduce the input, so we are interested in the order of the
    # attributess
    p.ordered_attributes = 1

    # Set our callbacks (we are stripping comments out by not defining
    # callbacks for them)
    p.XmlDeclHandler = xml_decl
    p.StartElementHandler = start_element
    p.EndElementHandler = end_element
    p.CharacterDataHandler = char_data

    global cur_file, cur_idx
    global out_dir, root, ext

    global FMT
    FMT = ".%%0%dd" % (int(log10(os.path.getsize(filename) / MAX_SIZE)) + 1)

    out_dir, filename = os.path.split(filename)
    if output_dir is not None:
        out_dir = output_dir

    root, ext = os.path.splitext(filename)

    cur_file = open(os.path.join(out_dir, root + FMT % cur_idx + ext), 'wt',encoding="utf8")

    with open(filename, 'rt', encoding="utf8") as xml_file:
        while True:
            # Read a chunk
            chunk = xml_file.read(CHUNK_SIZE)
            if len(chunk) < CHUNK_SIZE:
                # End of file
                # tell the parser we're done
                p.Parse(chunk, 1)
                # exit the loop
                break
            # process the chunk
            p.Parse(chunk)
            
    # Don't forget to close our handle
    cur_file.close()
    
    print("part %d Done" % cur_idx)

if __name__ == "__main__":
    parser = OptionParser(usage="usage: %prog [options] XML_FILE")
    parser.add_option("-o", "--output-dir",
        help="Specify the directory where the xml files will be written" \
            "(default to the same directory where the original file is)")
    parser.add_option("-M", "--max_size", type="int",
        help="Specify the size at which the files should be split (in Kb)")
    (options, args) = parser.parse_args()
    if len(args) != 1:
        parser.error("incorrect number of arguments")
    if options.max_size is not None:
        MAX_SIZE = options.max_size * 1024
    main(args[0], options.output_dir)

It has worked perfectly
You saved my day.
Thanks alot

This is the command I used after I get to the directory (cd command) which contain both xml_split.py and my xml file (arwiktionary.xml) :
python xml_split.py arwiktionary.xml -M 40000

The output files are:
arwiktionary.0.xml
arwiktionary.1.xml

Thanks again

Could you please help me o tried you use this code and I changed According to my requirements but still I got the last print message

Print (" error : incorrect number of arguments")

Thanks alot! Works for me!
python xml_split.py -o ./done/ -M 51200 AS_ADM_HIERARCHY.XML

I came back here to say THANK YOU! It worked perfectly on a huge XML with abstracts for a meta-analysis.

In case there are other python noobs out there (like myself) that want to use this script, just a clarification: you don't have to change anything in the code; you just have to run it on your IDE terminal or directly from the command line (choosing as directory the folder you have saved the script. Preferably, have the XML you want to modify in the same folder) using the following command (if you're on Windows): python script-name.py your-xml-filename.xml; and voilà: sub-files of the original XML are created in the same directory! For example, I ran python metAphasia.py Aphasia_final.xml. You can also edit the size of the XML batches by modifying the code on line 22 of the script (the default is to create 3MB batches, but you can change 3 to whatever suits your purpose best. I changed it to 30, and it worked fine, but I guess it would work with any batch size).