try — Expert Examples

Starts a block of code that will be monitored for exceptions

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Exception handling bytecode

How try/except compiles to bytecode.

python
import dis

def example():
    try:
        x = 1 / 0
    except ZeroDivisionError:
        return "caught"
    else:
        return "ok"
    finally:
        pass  # cleanup

dis.dis(example)

# Key bytecodes:
# SETUP_FINALLY - sets up the exception handler
# POP_EXCEPT - clears the exception state
# The finally block is duplicated in both paths

CPython uses SETUP_FINALLY to register exception handlers on an internal block stack. The finally block is compiled into both the normal and exception paths.

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