sys-settrace

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sys.settrace 为built-in函数

底层实现代码

sys.settrace 调用关系

  1. https://github.com/python/cpython/blob/master/Python/sysmodule.c
  2. https://github.com/python/cpython/blob/master/Python/ceval.c

PyFrameObject 实现

  1. https://github.com/python/cpython/blob/master/Include/frameobject.h
  2. https://github.com/python/cpython/blob/master/Objects/frameobject.c
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import sys


def trace_func(frame, event, arg):
    value = frame.f_locals["a"]
    if value % 2 == 0:
        value += 1
        frame.f_locals["a"] = value


def f(a):
    print(a)


if __name__ == "__main__":
    trace = sys.gettrace()
    sys.settrace(trace_func)
    for i in range(0, 5):
        f(i)
    sys.settrace(trace)