spring cleanup for QQbar

[chapoton]

removing one deprecated class (after #19954)

also fix most of the pep8 warnings

plus a few minor code improvements

[chapoton]

New commits:

​1303a1d

spring cleanup of QQbar (pep8, removing deprecated stuff)

[chapoton]

green bot, please review

[tscrim]

I do not understand the extras=None change. I think it is fine to have an optional parameter that has a default value as optional is a way to convey a little more context/information to the user (rather than saying it is a default value). If there is something that is passing None, then I feel that should be changed.

[chapoton]

The reason is the following (as explained by lgtm):

When a parameter default value is a dictionary, it is stored in the function definition, and any modification of this dictionary is acting on (changing) this stored default. So the next call of the function will use the modified default. Which is not the expected effect.

[tscrim]

I was not aware of that, but it makes sense that things were designed that way. That sure can lead to subtle bugs.

sage: def foo(x, d={}):
....:     d[x] = 1
....:     return d
....: 
sage: x = foo(5)
sage: x
{5: 1}
sage: x[10] = 10
sage: foo(0)
{0: 1, 5: 1, 10: 10}

However, in these cases the dict is only expanded and never changed. So I don't see the point of making the code more complex to silence a warning:

sage: def bar(**opts):
....:     opts[1] = 5
....:     
sage: def foo(d={}):
....:     bar(**d)
....:     return d
....: 
sage: foo()
{}
sage: foo()
{}

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​d24560a

trac 27443 change-back the extras parameter of completions in QQbar

[chapoton]

done, back to {}

[tscrim]

Thank you. LGTM.