juliacall now starts julia with one thread by default (#750)

Co-authored-by: Christopher Rowley <github.com/cjdoris>

Author: cjdoris

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 * Added `juliacall.TypeValue.__numpy_dtype__` attribute to allow converting Julia types
   to the corresponding NumPy dtype, like `numpy.dtype(jl.Int)`.
+* JuliaCall now launches Julia with 1 thread by default.
 * Bug fixes.
 
 ## 0.9.31 (2025-12-17)

pysrc/juliacall/__init__.py

@@ -152,7 +152,7 @@ def args_from_config(config):
     CONFIG['opt_optimize'] = choice('optimize', ['0', '1', '2', '3'])[0]
     CONFIG['opt_procs'] = int_option('procs', accept_auto=True)[0]
     CONFIG['opt_sysimage'] = sysimg = path_option('sysimage', check_exists=True)[0]
-    CONFIG['opt_threads'] = int_option('threads', accept_auto=True)[0]
+    CONFIG['opt_threads'] = option('threads', default='1')[0]
     CONFIG['opt_warn_overwrite'] = choice('warn_overwrite', ['yes', 'no'])[0]
     CONFIG['opt_handle_signals'] = choice('handle_signals', ['yes', 'no'])[0]
     CONFIG['opt_startup_file'] = choice('startup_file', ['yes', 'no'])[0]