Python 3.14+pdbfunction

pdb.set_default_backend()

backend

Sets the backend for new Pdb instances: 'settrace' (the default) or 'monitoring', built on sys.monitoring.

Syntax

pdb.set_default_backend(backend)

The 'monitoring' backend (PEP 669) barely slows code outside breakpoints, while 'settrace' traces every line. The setting affects only Pdb() instances created without backend=; breakpoint() and set_trace() always use 'monitoring'. Any other name raises ValueError. Added in Python 3.14.

Examples

import pdb
pdb.set_default_backend('monitoring')
print(pdb.Pdb(readrc=False).backend)  # → monitoring
try:
    pdb.set_default_backend('fast')
except ValueError as e:
    print(e)  # → Invalid backend: fast

See also

Common errors

Open in the full glossarydocs.python.orgReport an inaccuracy