Python implementation of side-by-side diff

sdiff.py

# Code licensed MIT  2023 Stefaan Lippens

import difflib
import itertools
from typing import List, Tuple, Iterator


class Sdiffer:
    def __init__(self, max_width:int = 80):
        # Two columns with a gutter
        self._col_width = (max_width - 3) // 2
        assert self._col_width > 0
        
    def _fit(self, s: str) -> str:
        s = s.rstrip()[:self._col_width]
        return  f"{s: <{self._col_width}}"

    def sdiff(self, a: List[str], b: List[str]) -> Iterator[str]:
        diff_lines = difflib.Differ().compare(a, b)
        diff_table: List[Tuple[str, List[str], List[str]]] = []
        for diff_type, line_group in itertools.groupby(diff_lines, key=lambda ln: ln[:1]):
            lines = [ln[2:] for ln in line_group]
            if diff_type == " ":
                diff_table.append((" ", lines, lines))
            else:
                if not diff_table or diff_table[-1][0] != "|":
                    diff_table.append(("|", [], []))
                if diff_type == "-":
                    # Lines only in `a`
                    diff_table[-1][1].extend(lines)
                elif diff_type == "+":
                    # Lines only in `b`
                    diff_table[-1][2].extend(lines)

        for diff_type, cell_a, cell_b in diff_table:
            for left, right in itertools.zip_longest(cell_a, cell_b, fillvalue=""):
                yield f"{self._fit(left)} {diff_type} {self._fit(right)}"
    
    def print_sdiff(self, a: List[str], b: List[str]) -> Iterator[str]:
        print("\n".join(self.sdiff(a, b)))

usage example:

dump_a = json.dumps(..., indent=2).splitlines(keepends=True)
dump_b = json.dumps(..., indent=2).splitlines(keepends=True)

Sdiffer().print_sdiff(dump_a, dump_b)

 {                                          {                                      
   "exp": 1680773344,                         "exp": 1680773344,                   
   "iat": 1680773044,                         "iat": 1680773044,                   
   "jti": "40410c7c-8828-4755-a5b8-fa09b |    "jti": "564abdb3-6e34-4a7c-b00e-77d1e
   "iss": "http://localhost:8642/realms/      "iss": "http://localhost:8642/realms/
   "aud": "account",                          "aud": "account",                    
   "sub": "7e7feab3-afd4-4186-a00c-c546a |    "sub": "d2aa0547-daaa-478b-9cb9-1ba2b
   "typ": "Bearer",                           "typ": "Bearer",                     
   "azp": "public-client-VQ5r6dli",      |    "azp": "service-client-L8FFS94R",    
   "session_state": "0c09bcad-45de-47ff- |    "preferred_username": "service-accoun
   "preferred_username": "user-c39y4yag" |                                         
   "email_verified": false,                   "email_verified": false,             
   "acr": "1",                                "acr": "1",                          
   "realm_access": {                          "realm_access": {                    
     "roles": [                                 "roles": [                         
       "default-roles-i168realm",                 "default-roles-i168realm",       
...