capi-sig December 2012

capi-sig@python.org

7 participants
23 discussions

Re: [capi-sig] Does Py_False or Py_True need de-referencing if used in a PyObject_Compare?

by Campbell Barton

It depends, sometimes you wont want to allow this for attribute assignment since it can be misleading. eg: foo.bar = [] On Tue, Dec 18, 2012 at 3:45 AM, Gustavo Carneiro <gjcarneiro(a)gmail.com> wrote: > You are not wrong. On the other hand, I often depend on the fact that an > empty list or dictionary is false, and true if not empty. It is quite > convenient, and I find it reasonably logical. > > On Mon, Dec 17, 2012 at 1:59 PM, Campbell Barton <ideasman42(a)gmail.com> > wrote: >> >> Take care using PyObject_IsTrue since it will accept many PyObject's >> (floats, lists, dicts etc), if you want to be strict with checking >> your input its not always so good. >> Instead you can use PyLong_AsLong() this works for True/False and any int >> type. >> >> eg: >> int param = PyLong_AsLong(value); >> if (param == -1 && PyErr_Occurred()) { >> .... error out ... >> } >> ... check the int now ... >> >> On Mon, Dec 17, 2012 at 10:23 PM, Gustavo Carneiro <gjcarneiro(a)gmail.com> >> wrote: >> > PyObject_IsTrue( >> >> >> >> -- >> - Campbell >> _______________________________________________ >> capi-sig mailing list >> capi-sig(a)python.org >> http://mail.python.org/mailman/listinfo/capi-sig > > > > > -- > Gustavo J. A. M. Carneiro > "The universe is always one step beyond logic." -- Frank Herbert -- - Campbell

8 years, 10 months

Looking for an opportunity to work with the Python CAPI

by Robert Steckroth

I apologize if this post is a little spamy, but if there are any professionals who can point me towards a starting position in regards to this industry, I would be grateful. If not, what type of companies use the Python CAPI? -- Bust0ut, Surgemcgee: Systems Engineer --- surgemcgee.com Django_Teamplate3d

8 years, 10 months

Re: [capi-sig] Does Py_False or Py_True need de-referencing if used in a PyObject_Compare?

by Gustavo Carneiro

You are not wrong. On the other hand, I often depend on the fact that an empty list or dictionary is false, and true if not empty. It is quite convenient, and I find it reasonably logical. On Mon, Dec 17, 2012 at 1:59 PM, Campbell Barton <ideasman42(a)gmail.com>wrote: > Take care using PyObject_IsTrue since it will accept many PyObject's > (floats, lists, dicts etc), if you want to be strict with checking > your input its not always so good. > Instead you can use PyLong_AsLong() this works for True/False and any int > type. > > eg: > int param = PyLong_AsLong(value); > if (param == -1 && PyErr_Occurred()) { > .... error out ... > } > ... check the int now ... > > On Mon, Dec 17, 2012 at 10:23 PM, Gustavo Carneiro <gjcarneiro(a)gmail.com> > wrote: > > PyObject_IsTrue( > > > > -- > - Campbell > _______________________________________________ > capi-sig mailing list > capi-sig(a)python.org > http://mail.python.org/mailman/listinfo/capi-sig > -- Gustavo J. A. M. Carneiro "The universe is always one step beyond logic." -- Frank Herbert

8 years, 10 months

Re: [capi-sig] Does Py_False or Py_True need de-referencing if used in a PyObject_Compare?

by Campbell Barton

Take care using PyObject_IsTrue since it will accept many PyObject's (floats, lists, dicts etc), if you want to be strict with checking your input its not always so good. Instead you can use PyLong_AsLong() this works for True/False and any int type. eg: int param = PyLong_AsLong(value); if (param == -1 && PyErr_Occurred()) { .... error out ... } ... check the int now ... On Mon, Dec 17, 2012 at 10:23 PM, Gustavo Carneiro <gjcarneiro(a)gmail.com> wrote: > PyObject_IsTrue( -- - Campbell

8 years, 10 months

Re: [capi-sig] Does Py_False or Py_True need de-referencing if used in a PyObject_Compare?

by Gustavo Carneiro

On Thu, Dec 13, 2012 at 4:21 PM, Robert Steckroth <robertsteckroth(a)gmail.com > wrote: > Does the below statement have a memory leak? > > if ( PyObject_Compare(update_var, Py_False) > > Do I need to assign the Py_False first and DECREF it, or is the above > snippet ok alone. > It's safe, but note that it is more correct to use PyObject_IsTrue: there are more values that can be considered true or false, besides python's True and False objects. if (!PyObject_IsTrue(update_var)) { ... } -- Gustavo J. A. M. Carneiro "The universe is always one step beyond logic." -- Frank Herbert

8 years, 10 months

Re: [capi-sig] How do I get the Objects to clean up after a python script exits?

by Campbell Barton

On Thu, Dec 13, 2012 at 5:45 AM, Robert Steckroth <robertsteckroth(a)gmail.com> wrote: > When I test my module in the interpreter it automatically cleans up any > created objects. This is a very nice feature > for my module and I would like to use it. How do I go about getting > my scripts to send an exit cleanup single? > > -- > Bust0ut, Surgemcgee: Systems Engineer --- > surgemcgee.com > Django_Teamplate3d > _______________________________________________ > capi-sig mailing list > capi-sig(a)python.org > http://mail.python.org/mailman/listinfo/capi-sig Heres an example of using atexit from C/Python api. (py3.x) https://svn.blender.org/svnroot/bf-blender/trunk/blender/source/blender/pyt… -- - Campbell

8 years, 10 months

Re: [capi-sig] Does Py_False or Py_True need de-referencing if used in a PyObject_Compare?

by Campbell Barton

On Fri, Dec 14, 2012 at 3:21 AM, Robert Steckroth <robertsteckroth(a)gmail.com> wrote: > Does the below statement have a memory leak? > > if ( PyObject_Compare(update_var, Py_False) > > Do I need to assign the Py_False first and DECREF it, or is the above > snippet ok alone. The python api docs will often say if they use/steal references. If your not sure you could just printf("%d\n", Py_REFCNT(Py_False)); before and after calling.

8 years, 10 months

Re: [capi-sig] Does Py_False or Py_True need de-referencing if used in a PyObject_Compare?

by Stefan Behnel

Robert Steckroth, 13.12.2012 17:57: > Well, from what I have gathered, the reference count does not need to be > maintain as far as PyBool objects go. They are like any other object, i.e. they need reference counting. > It seem to be fine even if the object is set from a argument. Hmmm... That's a different case. As long as you are sure that someone (better you) owns a reference to the object that you pass as argument, you don't need to increase its refcount just for the call. That's easy to get wrong, though. >> Does the below statement have a memory leak? >> >> if ( PyObject_Compare(update_var, Py_False) Why should it? >> Do I need to assign the Py_False first and DECREF it, or is the above >> snippet ok alone. I keep being surprised by what some people take their fun in programming from. Good to see that you're getting actual functionality done regardless. Stefan

8 years, 10 months

Re: [capi-sig] How do I get the Objects to clean up after a python script exits?

by Stefan Behnel

Robert Steckroth, 12.12.2012 19:45: > When I test my module in the interpreter it automatically cleans up any > created objects. This is a very nice feature > for my module and I would like to use it. How do I go about getting > my scripts to send an exit cleanup single? Depends on exactly what you are trying to achieve, but you might want to look at the atexit module. Py3 additionally has the PyModuleDef setup which allows you to clean up module globals at exactly the right time on interpreter tear down. It basically implements garbage collection for modules. (Shameless hint: Cython cleans up global variables for you automatically and chooses the right way to do so based on the capabilities of the current runtime.) Stefan

8 years, 10 months

Re: [capi-sig] How do I get the Objects to clean up after a python script exits?

by Stefan Behnel

8 years, 10 months

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capi-sig December 2012