I used to do some of this, and have a few books out.
It's an incredibly varied field, with a lot of different routes into it. The main markets are:
Print magazines
Online magazines/blogs/sites
Formal corporate technical writing
Mainstream tech publishing
DIY tech publishing
They all have different requirements, schedules, and working relationships.
The first two are probably the easiest to get into. If you have no experience, write a couple of polished sample pieces, and then start contacting editors with ideas that match the magazine/blog. Send in the samples when they ask for them. Mention the Python book too. If you can build a relationship and are good, you will get regular work.
Beware - good writing is harder than it looks. You have to be accurate, concise, and entertaining as well as informative. You may also have to be fast. Payment varies from not much at all to - exceptionally - high four figures at the very top end for high profile journalism.
Formal tech writing is a very specific skill and it's hard to get a job in it without some previous experience and/or a basic qualification. I've never done it so I don't know how to get into it.
Mainstream publishing - list the publishers (there aren't many in tech), find the commissioning editors, and email them with a couple of suggestions for books. Mention the Python book. If you get interest you will probably get an advance - high four to very low five figures is usual for niche tech, maybe double that for consumer tech. Don't accept a project that offers less, because it won't be worth the time. Formatting and editing for print can be torturously specific, so it's not so fun from that POV.
DIY - Leanpub is a popular platform. So is Createspace. Marketing will kill you, so you'll have to do a lot of it. Putting up a marketing site is not enough. Email lists are your friend.
Generally writing doesn't pay nearly as well as coding. I did it for a while after burning out on writing too many projects in assembler in the late 80s and early 90s. It was great for a period, and I had a couple of years where I could have lived off royalty payments. The market now is much broader but much shallower - many more opportunities, but mostly they don't pay nearly as well.
Like other people, I've sometimes used mainstream pub as a way to get paid to learn. You have to pay that back with a book, but it's not a bad deal compared to not getting paid to learn.