It does suck for beginners who end up having to know about all variations until their usage drops off.

The other ones at least are based on the same format string syntax.

"foo {}".format("bar") would be an obvious "just use f-string" case, except when the formatting happens far off. But in that case you could "just" use t-strings? Except in cases where you're (for example) reading a format string from a file. Remember, t- and f- strings are syntactic elements, so dynamism prevents usage of it!

So you have the following use cases:

- printf-style formatting: some C-style string formatting is needed

- .format: You can't use an f- string because of non-locality in data to format, and you can't use a t- string due to dynamism in

- f-string: you have the template and the data in the same spot lexicographically, and you just want string concatenation (very common!)

- t-string: you have the template and the data in the same spot lexicogrpahically, but want to use special logic to actually build up your resulting value (which might not even be a string!)

The last two additions being syntax makes it hard to use them to cover all use cases of the first two.

But in a specific use case? It's very likely that there is an exact best answer amongst these 4.

I see (4) being about the flexibility of (2) and readability of (3). Maybe it'll eventually grow to dominate one or both, but it's also fine if it doesn't. I don't see (1) going away at all since the curly collision still exists in (4).

    import string
    t = string.Template("foo $bar")
    t.substitute(bar="bar")

log.error("foo happend %s", reason)