Change the width of difflib.make_file() HTML Table?

You can use wrapcolumn= in HtmlDiff

import difflib
import webbrowser

d = difflib.HtmlDiff(wrapcolumn=10)

lines1 = ['aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa']
lines2 = ['XXXXXXXXXXXXXaaaaaaaaaYYYaaaaaaZZZZZZZZZZZaaaaZZZZZZZZ']

html = d.make_file(lines1, lines2)

with open('output.html', 'w') as fh: 
    fh.write(html)

webbrowser.open('output.html')

Without wrapcolumn=

With wrapcolumn=10

EDIT:

I didn't test it but in source code of diff you can see hidden variables _styles, _table_template, _file_template which you could replace in HtmlDiff to generate different HTML. This way you could add classes and styles to format it.

It may also need to change hidden _format_line to remove nowrap="nowrap"

EDIT:

I use HtmlDiff to create own class with new _format_line() without nowrap="nowrap" and now I can add styles with width and word-break

import difflib
import webbrowser

# --- classes ---

class MyHTML(difflib.HtmlDiff):

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
   
        # append new styles inside new class 
        self._styles = self._styles + """
table.diff {width: 300px}
.diff_sub {display: inline-block; word-break: break-word;}
.diff_add {display: inline-block; word-break: break-word;}
"""

    # function from source code - I remove only `nowrap="nowrap"`
    def _format_line(self,side,flag,linenum,text):
        """Returns HTML markup of "from" / "to" text lines
        side -- 0 or 1 indicating "from" or "to" text
        flag -- indicates if difference on line
        linenum -- line number (used for line number column)
        text -- line text to be marked up
        """
        try:
            linenum = '%d' % linenum
            id = ' id="%s%s"' % (self._prefix[side],linenum)
        except TypeError:
            # handle blank lines where linenum is '>' or ''
            id = ''
        # replace those things that would get confused with HTML symbols
        text=text.replace("&","&amp;").replace(">","&gt;").replace("<","&lt;")

        # make space non-breakable so they don't get compressed or line wrapped
        text = text.replace(' ','&nbsp;').rstrip()

        return '<td class="diff_header"%s>%s</td><td>%s</td>' \
               % (id,linenum,text)

# --- main ---

d = MyHTML()

# >>> changing styles after creating `MyHTML` or in original `HtmlDiff <<<
#d._styles = d._styles + """
#table.diff {width: 300px}
#.diff_sub {display: inline-block; word-break: break-word;}
#.diff_add {display: inline-block; word-break: break-word;}
#"""

#d._file_template = """new template"""
    

lines1 = ['aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa']
lines2 = ['XXXXXXXXXXXXXaaaaaaaaaYYYaaaaaaZZZZZZZZZZZaaaaZZZZZZZZ']

html = d.make_file(lines1, lines2)

with open('output.html', 'w') as fh: 
    fh.write(html)

webbrowser.open('output.html')

Shorter version

import difflib
import webbrowser

d = HtmlDiff(wrapcolumn=10)

d._file_template = """new template with %(charset)s %(styles)s %(table)s %(legend)s"""         
#d._styles = """new styles"""         

lines1 = ['aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa']
lines2 = ['XXXXXXXXXXXXXaaaaaaaaaYYYaaaaaaZZZZZZZZZZZaaaaZZZZZZZZ']

html = d.make_file(lines1, lines2)

with open('output.html', 'w') as fh: 
    fh.write(html)

webbrowser.open('output.html')