raise — Expert Examples

Throws an exception manually

EasyIntermediateAdvancedExpert

Raise bytecode and exception internals

How raise works under the hood.

python
import dis

def raise_explicit():
    raise ValueError("test")

def raise_bare():
    try:
        1/0
    except:
        raise

def raise_from():
    try:
        1/0
    except ZeroDivisionError as e:
        raise RuntimeError("wrapped") from e

print("raise ValueError('test'):")
dis.dis(raise_explicit)
print("\nbare raise:")
dis.dis(raise_bare)
print("\nraise ... from ...:")
dis.dis(raise_from)

raise compiles to RAISE_VARARGS with 1 arg (exception), bare raise uses 0 args (re-raise), and 'raise from' uses 2 args (exception + cause).

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