Seat posts - interchangeable?

[Cldy]

Super newbie here. Apologies if my question is too dumb!
I'm trying to pick up cycling again however find that the smallest 17" frame bicycles have seat posts that are just a bit too high for me to be comfortable. The posts are already at the lowest setting. It was suggested that to ease into cycling, perhaps I should get a seat post without suspension and so the seat can be lower by 1-2 inches which will be just nice for me and will not be as daunting because I can then touch the ground when seated. I'm quite keen on this as I'm a bit apprehensive if I can't feel the ground. I've looked around online and it seems most 27.2mm diameter seat posts are 40cm in length which is too high. I've found a few that are 35cm but not ideal. I saw one seat post on c r c which is 30cm in length and this will actually be just right. So my question is, are different brands of (basic) seat posts interchangeable? Is 30cm too short as I only found one and only one seat post at that length?

Many thanks in advance!

[Baalzamon]

You need to make sure that the seatpost diameter is the same as well! It should be stamped somewhere on your current seatpost indicating diameter. Using that you can find another seatpost to match it.

[yugyug]

If your saddle is low enough that you can have your feet flat on the ground while seated, it's to low for a comfortable pedaling position.

[RonK]

If your saddle is low enough that you can have your feet flat on the ground while seated, it's to low for a comfortable pedaling position.

In other words, sore/damaged knees may well be the result.

When you stop, get off the saddle.

[Cldy]

Thank you everyone for your replies.
Yugyug and RonK, I'm sure the current fit is correct. The problem lies with my low confidence and the fact that I haven't actively ridden in 20 years so to be on the road without the "safety" of touching the ground, I feel very apprehensive. At the moment when seated, I can't touch the ground and when on the bike, it feels comfortable. Problem lies when stopping! I want to build up my confidence first and then change back to the original seat post once I'm comfortable/confident enough to go onto roads and do longer distances. Does that make sense?

The part of the seat posts that attaches to the saddle is usually generic yes? So I can just buy one with the correct diameter and length?

Many thanks again. I hope to be able to cycle longer distances with the ultimate aim of commuting (ie cycle with traffic).

[bychosis]

Sounds like the best option is to find a nice quiet area and practice your stopping. You should be aiming to come to a stop and either tip the bike to the side while on the seat (disconcerting for a novice) or a better option is as you approach your stop put your right pedal to the bottom and stand and move forward off your saddle to straddle the frame. A little more practice and you won't need to worry about the seatpost, it needs to be right for riding, not when you are stopped.

[yugyug]

The part of the seat posts that attaches to the saddle is usually generic yes? So I can just buy one with the correct diameter and length?

).

Yes.

In regards to moving from a seated position to a standing position when stopping, I suppose the thing to practice is both stopping slowly and suddenly (with emergency braking). Feel how natural it is to simply slide off the seat forward so that your are standing astride the bike over the top bar when fully stopped. I would go practice this first on a nice soft grassy area before bothering to change your seat post. Though I'm also wondering why you have a suspension seat post as it doesn't sound really necessary for the kind of riding you say you will be doing, not that it really matters.

[Cldy]

Thank you very much. You have all made really good points and saved me $50. Practice practice I shall!