Python bindings: Account.getName() raises TypeError

[John Ralls]

On Mar 17, 2014, at 10:52 AM, Derek Atkins <warlord at mit.edu> wrote:

> John Ralls <jralls at ceridwen.us> writes:
> 
>>> TypeError: in method 'xaccAccountGetName', argument 1 of type
>>> Account const *'
> [snip]
>> 
>> The signature of xaccAccountGetName is const char* xaccAccountGetName
>> (const Account *); the const was added in 2005. A "const Account *" is
>> not the same as an "Account const *": The former means that the
>> contents of the pointer won't change, the latter means that the
>> pointer itself won't change (see
>> https://www.cs.bu.edu/teaching/cpp/const/).
>> 
>> Somewhere in the SWIG-generated Python-to-C translation code the
>> argument type is wrong, but it's not directly in the stack trace from
>> Python. It's more likely due to a change in SWIG than to a change in
>> GnuCash.
> 
> Could it be a const v non-const issue?  I.e., if python has an Account*
> object (non-const) does it realize that it can pass it to a function
> that is asking for a const object (either const Account* or Account
> const * -- doesn't matter)?  C certainly knows this, but it sounds like
> Python might not.

At that level, it’s all C; in this case it’s C generated by SWIG instead of written by hand, but it’s still C.

Python doesn’t even have the concept of const, and its handling of types is deliberately generic: If an object has a member with the right name, it’s happy.

Regards,
John Ralls