[feature] Add __contains__ into PyRequires

[andrey-zherikov]

What is your suggestion?

This request came up from working on renaming "python_requires" package (see #20076 for reference).

My "python_requires" package (let call it my-package) provides a class (let call it MyRecipe) that used through python_requires_extend. This MyRecipe class accesses self.python_requires["my-package"].path and this expression must be changed to support new and old names.

My current solution is to do this:

if 'my-package' in dict(self.python_requires.items()):
    use(self.python_requires['my-package'].path)
else:
    use(self.python_requires['my-new-package'].path)

However it would be better way to simply do this:

if 'my-package' in self.python_requires:
    use(self.python_requires['my-package'].path)
else:
    use(self.python_requires['my-new-package'].path)

Have you read the CONTRIBUTING guide?

• I've read the CONTRIBUTING guide

[memsharded]

Hi @andrey-zherikov

Thanks for the feedback.

Why not using the Pythonic way with:

try:
    use(self.python_requires['my-package'].path)
except ConanException:
    use(self.python_requires['my-new-package'].path)

That is even simpler than doing the if, and good Python practices point in this direction instead of using if conditions.

[andrey-zherikov]

ConanException is more generic than KeyError and can contain any error happened inside conan source so it's not quite correct. I also can't use except KeyError either because of this.

[memsharded]

As the implementation of __getitem__ is

    def __getitem__(self, item):
        try:
            return self._pyrequires[item]
        except KeyError:
            raise ConanException("'%s' is not a python_require" % item)

the following:

try:
    pyreq = self.python_requires['my-package']
except ConanException:
    pyreq = self.python_requires['my-new-package']

use(pyreq.path)

should be pretty idiomatic