db-process

Python interface to DesignBuilder's command-line driver — typed /process= commands, subprocess execution, process discovery, and diagnostics-log parsing.

DesignBuilder is a Windows GUI app, but it exposes a /process= argument that runs a sequence of commands non-interactively and exits. db-process wraps that surface in real Python: dataclass commands instead of stringly-typed flags, a ProcessChain builder, blocking and non-blocking runners, helpers to find/kill the process, and a parser for the rolling diagnostics logs DesignBuilder writes under %LOCALAPPDATA%.

Install

pip install db-process
# or, from the cloned repo:
pip install -e .[dev]

Requires Python 3.10+ and psutil. DesignBuilder itself only runs on Windows; on other platforms, the package imports fine but run() and the process helpers will raise FileNotFoundError.

Quick start

Python — run a model with a chain of commands

from db_process import ProcessChain, Screen, run

chain = (
    ProcessChain()
    .use_sim_manager()
    .switch_screen(Screen.SIMULATION)
    .sim_start_date(1, 1)
    .sim_end_date(31, 12)
    .change_attribute("OccupancyValue", 0.5)
    .run()
)

result = run("models/office.dsb", chain, timeout=600)
print(result.success, result.duration_seconds)

Python — convenience factories for common runs

from db_process import eplus_simulation, run

# A pre-built ProcessChain for "open model, run EnergyPlus, close".
result = run("models/office.dsb", eplus_simulation())

Other factories: sbem_calculation, export_xml, heating_and_cooling_design, daylighting, cfd_simulation.

Python — non-blocking with idle-detection kill

from db_process import run_async

handle = run_async("models/office.dsb")
# Block until DesignBuilder finishes its work and CPU drops, then kill it.
handle.kill_when_idle(idle_threshold=10, cpu_threshold=0.1)

kill_when_idle is the workaround for runs where DesignBuilder finishes the calculation but doesn't exit — common with the GUI Sim Manager path.

CLI

db-process status              # is DesignBuilder running? show pid + exe path
db-process open                # launch DesignBuilder
db-process open path/to.dsb    # launch with a model
db-process close               # kill any running DesignBuilder
db-process restart [model]     # close + open (with a 1.5 s settle)

db-process diag list           # list recent diagnostic logs (newest first)
db-process diag latest         # print a one-paragraph summary of the newest log
db-process diag latest --errors   # also list every error line found
db-process diag summary <path>    # summarise a specific log

db-process is the entry point installed by the package; you can also run it as python -m db_process.

Public API

from db_process import (
    # Executable discovery
    find_designbuilder,                          # () -> Path

    # Process status
    is_running, find_process, status,            # status() -> ProcessStatus
    kill_process, kill_when_idle,
    ProcessStatus,                               # is_running, pid, exe_path

    # Run
    run, run_async, RunHandle, RunResult,

    # Command model
    ProcessChain, Screen,
    SwitchScreen, RunCalculation, TabChange,
    SimStartDate, SimEndDate, ChangeAttributeValue,
    ExternalCommand, ImportModelData, ImportLibraryData,
    ExportAsXML, UseSimManager, NoClose,

    # Convenience factories
    eplus_simulation, sbem_calculation, export_xml,
    heating_and_cooling_design, daylighting, cfd_simulation,

    # Diagnostics logs
    DiagnosticsLog, find_logs, latest_log,
    parse_filename_timestamp, DEFAULT_DIAGNOSTICS_DIR,
)

Executable discovery

find_designbuilder(exe_path=None) resolves DesignBuilder.exe in this order:

1. The explicit exe_path argument, if given.
2. DESIGNBUILDER_EXE environment variable.
3. C:\Program Files (x86)\DesignBuilder\DesignBuilder.exe, then C:\Program Files\DesignBuilder\DesignBuilder.exe.
4. The system PATH (shutil.which("DesignBuilder")).

Raises FileNotFoundError with a hint to set DESIGNBUILDER_EXE if none match.

Process status

status() is a one-shot snapshot:

from db_process import status

s = status()
# ProcessStatus(is_running=True, pid=12345, exe_path='C:\\...\\DesignBuilder.exe')
if not s.is_running and s.exe_path:
    # Discovered but not running — safe to launch.
    ...

exe_path is populated regardless of whether the process is running, so callers can decide whether to launch without a second find_designbuilder call.

ProcessChain — building a /process= argument

ProcessChain is a fluent builder for the /process= command sequence documented in DesignBuilder Help. Example output of chain.to_string():

/process=UseSimManager, miGSS, SimStartDate 1 1, SimEndDate 31 12,
         ChangeAttributeValue OccupancyValue 0.5, miTUpdate

Every command is also exposed as a plain dataclass, so you can construct chains without the builder when that's clearer.

Diagnostics logs

DesignBuilder writes a per-session diagnostics log to %LOCALAPPDATA%\DesignBuilder\Diagnostics\ named like DesignBuilder_diagnostic_2026-04-23_15-12-08.txt. DiagnosticsLog parses one of those files into a structured object:

from db_process import latest_log, DiagnosticsLog

log = DiagnosticsLog.from_file(latest_log())
print(log.summary())
print(log.is_complete, log.duration, log.error_count)
for line_no, text in log.errors:
    print(f"L{line_no}: {text}")

Error detection uses word-boundary matching (error, failed, exception, fatal, crash) plus a small negative list to suppress known benign markers (e.g. the GL_KHR_no_error OpenGL extension).

Compatibility

• DesignBuilder: any version that supports the /process= argument. Tested against the v25.1 / v26.1 lines.
• Python: 3.10+.
• OS: Windows for live runs. The command model and diagnostics parser are pure Python and import on any platform — useful for unit tests on Linux CI.

Development

pip install -e .[dev]
pytest         
ruff check .

Tests are split by area:

File	Covers
test_commands.py	ProcessChain building + every command's to_string()
test_executable.py	find_designbuilder resolution order
test_status.py	status / ProcessStatus
test_diagnostics.py	log parsing, error detection, filename timestamps
test_cli.py	CLI argparse wiring (mocked subprocess)