[Python-Dev] Changing a value in a frame (for a debugger) (original) (raw)

Fabio Zadrozny fabiofz at gmail.com
Wed Feb 7 11:11:36 CET 2007

On 2/7/07, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:

Fabio Zadrozny wrote: > frame = findFrame(threadid, frameid) > exec '%s=%s' % (attr, expression) in frame.fglobals, frame.flocals The locals of a function are actually stored in an array. When you access them as a dict using locals(), all you get is a dict containing a copy of their current values. Modifying that dict doesn't affect the underlying array. It seems that reading the flocals of a frame does the same thing. To modify the locals, you would need to poke values into the original array -- but it doesn't seem to be exposed to Python. So it looks like you're out of luck.

Would it be ok to add a feature request for that? I initially thought it was completely read-only, but I find it strange that it affects the topmost frame correctly (so, it seems that even though I get a copy, when I alter that copy on the topmost frame it affects it correctly)... anyone has a clue why that happens?

It seems to affect pdb too...

Consider the code: if name == 'main':

def call1():
    v_on_frame1 = 10
    print 'v_on_frame1', v_on_frame1

def call0():
    import pdb;pdb.set_trace()
    v_on_frame0 = 10
    call1()
    print 'v_on_frame0', v_on_frame0

call0()

#when modifying in the current frame

x:\scbr15\source\python\testsbase\emptytest.py(9)call0() -> v_on_frame0 = 10 (Pdb) n x:\scbr15\source\python\testsbase\emptytest.py(10)call0() -> call1() (Pdb) v_on_frame0 = 40 (Pdb) c v_on_frame1 10 v_on_frame0 40

#when modifying an upper frame it does not work

x:\scbr15\source\python\testsbase\emptytest.py(9)call0() -> v_on_frame0 = 10 (Pdb) n x:\scbr15\source\python\testsbase\emptytest.py(10)call0() -> call1() (Pdb) s --Call-- x:\scbr15\source\python\testsbase\emptytest.py(3)call1() -> def call1(): (Pdb) n x:\scbr15\source\python\testsbase\emptytest.py(4)call1() -> v_on_frame1 = 10 (Pdb) u x:\scbr15\source\python\testsbase\emptytest.py(10)call0() -> call1() (Pdb) v_on_frame0 = 40 (Pdb) d x:\scbr15\source\python\testsbase\emptytest.py(4)call1() -> v_on_frame1 = 10 (Pdb) c v_on_frame1 10 v_on_frame0 10 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://mail.python.org/pipermail/python-dev/attachments/20070207/89e064ec/attachment.html

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