Perhaps these source references are useful: Python/ceval.c (_PyEval_EvalFrameDefault) https://github.com/python/cpython/blob/main/Python/ceval.c#L3754-L3768 Objects/object.c (do_richcompare) https://github.com/python/cpython/blob/42fee931d055a3ef8ed31abe44603b9b2856e04d/Objects/object.c#L661-L713
Kind regards, Sam Ezeh On Fri, 6 May 2022 at 18:12, Jonathan Kaczynski <jonathan.kaczyn...@guildeducation.com> wrote: > > Hi, > > I was recently trying to explain how python equality works and ran into a > gap in my knowledge. I haven't found any good pages going beneath a surface > level explanation of python equality comparison. > > I'll post my investigations below. What I think I'm looking for is where in > the source code (https://github.com/python/cpython) does the equality > comparison occur. I have an idea but wanted to ask first. > > > Using the dis module, we see the comparison operator is a single bytecode, > which is expected. > > ❯ docker run -it --rm ubuntu:jammy > root@919d94c98191:/# apt-get update > root@919d94c98191:/# apt-get --yes install python3 > root@919d94c98191:/# cat >play.py <<EOF > import dis > import uuid > > def test(): > x = uuid.uuid4() > y = str(x) > x == y > return > > dis.dis(test) > EOF > root@f33b02fef026:/# python3 play.py > ... snip ... > 7 16 LOAD_FAST 0 (x) > 18 LOAD_FAST 1 (y) > 20 COMPARE_OP 2 (==) > 22 POP_TOP > ... snip ... > > > Stepping through the code with gdb, we see it jump from the compare > operator to the dunder-eq method on the UUID object. What I want to be able > to do is explain the in-between steps. Also, if you change `x == y` to `y > == x`, you still see the same behavior, which I assume has to do with > dunder-eq being defined on the UUID class and thus given priority. > > ❯ docker run -it --rm ubuntu:jammy > root@919d94c98191:/# apt-get update > root@919d94c98191:/# apt-get --yes install dpkg-source-gitarchive > root@919d94c98191:/# sed -i 's/^# deb-src/deb-src/' /etc/apt/sources.list > root@919d94c98191:/# apt-get update > root@919d94c98191:/# apt-get --yes install gdb python3.10-dbg > root@919d94c98191:/# apt-get source python3.10-dbg > root@919d94c98191:/# cat >play.py <<EOF > import uuid > x = uuid.uuid4() > y = str(x) > breakpoint() > x == y > EOF > root@919d94c98191:/# gdb python3.10-dbg > (gdb) dir python3.10-3.10.4/Python > (gdb) run play.py > Starting program: /usr/bin/python3.10-dbg play.py > > warning: Error disabling address space randomization: Operation not > permitted > [Thread debugging using libthread_db enabled] > Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". > > //play.py(5)<module>() > -> x == y > (Pdb) s > --Call-- > > /usr/lib/python3.10/uuid.py(239)__eq__() > -> def __eq__(self, other): > > > Thank you, > Jonathan > -- > https://mail.python.org/mailman/listinfo/python-list -- https://mail.python.org/mailman/listinfo/python-list
