Fixed "UnsupportedOperation" exception in highs_api.py

[postlogist]

This patch solves two issues in HiGHS API (actualSolve method): 1) Code for parsing a list of additional options had a typo in method name (should be startswith) 2) The new method of starting a subprocess caused UnsupportedOperation exception in Windows (tested with Anaconda Python and WinPython). I replaced this code with the code from PuLP 2.7.0 release.

Here's the stack trace for the error that previously appeared --------------------------------------------------------------------------- UnsupportedOperation Traceback (most recent call last) Cell In[30], line 1 ----> 1 prob.solve(solver=highs) 2 print(f"Status: {pl.LpStatus[prob.status]}") 3 print(f"EV = {-pl.value(prob.objective): .0f}")

File ~.conda\envs\opt\Lib\site-packages\pulp\pulp.py:1920, in LpProblem.solve(self, solver, kwargs) 1918 # time it 1919 self.startClock() -> 1920 status = solver.actualSolve(self, kwargs) 1921 self.stopClock() 1922 self.restoreObjective(wasNone, dummyVar)

File ~.conda\envs\opt\Lib\site-packages\pulp\apis\highs_api.py:145, in HiGHS_CMD.actualSolve(self, lp) 143 with open(tmpOptions, "w") as options_file: 144 options_file.write("\n".join(file_options)) --> 145 process = subprocess.run(command, stdout=sys.stdout, stderr=sys.stderr) 147 # HiGHS return code semantics (see: https://github.com/ERGO-Code/HiGHS/issues/527#issuecomment-946575028) 148 # - -1: error 149 # - 0: success 150 # - 1: warning 151 if process.returncode == -1:

File ~.conda\envs\opt\Lib\subprocess.py:548, in run(input, capture_output, timeout, check, *popenargs, *kwargs) 545 kwargs['stdout'] = PIPE 546 kwargs['stderr'] = PIPE --> 548 with Popen(popenargs, **kwargs) as process: 549 try: 550 stdout, stderr = process.communicate(input, timeout=timeout)

File ~.conda\envs\opt\Lib\subprocess.py:992, in Popen.init(self, args, bufsize, executable, stdin, stdout, stderr, preexec_fn, close_fds, shell, cwd, env, universal_newlines, startupinfo, creationflags, restore_signals, start_new_session, pass_fds, user, group, extra_groups, encoding, errors, text, umask, pipesize, process_group) 973 raise ValueError(f"User ID cannot be negative, got {uid}") 975 # Input and output objects. The general principle is like 976 # this: 977 # (...) 987 # are -1 when not using PIPEs. The child objects are -1 988 # when not redirecting. 990 (p2cread, p2cwrite, 991 c2pread, c2pwrite, --> 992 errread, errwrite) = self._get_handles(stdin, stdout, stderr) 994 # From here on, raising exceptions may cause file descriptor leakage 995 996 # We wrap OS handles before launching the child, otherwise a 997 # quickly terminating child could make our fds unwrappable 998 # (see #8458). 1000 if _mswindows:

File ~.conda\envs\opt\Lib\subprocess.py:1384, in Popen._get_handles(self, stdin, stdout, stderr) 1381 c2pwrite = msvcrt.get_osfhandle(stdout) 1382 else: 1383 # Assuming file-like object -> 1384 c2pwrite = msvcrt.get_osfhandle(stdout.fileno()) 1385 c2pwrite = self._make_inheritable(c2pwrite) 1387 if stderr is None:

File ~.conda\envs\opt\Lib\site-packages\ipykernel\iostream.py:311, in OutStream.fileno(self) 309 return self._original_stdstream_copy 310 else: --> 311 raise io.UnsupportedOperation("fileno")

UnsupportedOperation: fileno

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[pchtsp]

I'm closing as this was solved in the latest PR