The former Scottish Conservative leader – who is due to join the House of Lords – said her commitments to her family mean she will not take on any “big jobs” until her son is in school.
Ms Davidson, who is no longer an MSP, spoke to Matt Chorley on Times Radio.
She said she is looking for new projects to work on while in the Lords.
Asked if she will take on the role of Scottish Secretary, Ms Davidson said there is “not a chance”.
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Giving two reasons for that response, she said: “One, because Alister Jack is doing the job of Scottish Secretary very well, thank-you very much.
“Two, because I promised my partner when I stepped away two years ago that I wouldn’t do any big jobs until my son – and if we’re blessed with any other younger brothers or sisters for them – are in school. And I intend to keep that promise.
“Lord knows in 10 years on the political frontline I have broken enough promises to my friends and family. But that’s one I intend to keep.
“And also because of my political journey of becoming the leader in Holyrood.
“Basically, as soon as I got elected, I missed out on and I didn’t learn my trade on the backbenches.
“And I made lots of mistakes because of that. And I’m actually looking, when I go to the Lords, to pick some projects to work on, to do some good work, and to learn.
“And actually at the age of 42, I’m going to really enjoy learning again.”
Asked what she thinks of the Prime Minister, she said: “I think Boris Johnson is a very likable guy when you’re in his company.
“He’s affable, he’s humorous, he’s intelligent, he’s warm.
“He’s a very forgiving man, you’ll see how many people he’s invited back.”