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Comment by rdtsc | Hacker News Reader

> However, once you start using several parameters and longer strings, your code will quickly become much less easily readable [...] `"Hello, %s %s. You are %s. You are a %s ...`

Minor correction: % formatting allows specifying names for dictionary keys too:

    In [1]: "%(a)s and %(b)s" % {"a":"A", "b":"B"}
    Out[1]: 'A and B'

In fact I had never switched to using str.format as it just never added enough benefit for me over the old %-based formatting.

But I do like f-strings and am using them quite a bit. Calling functions or methods inside f-strings is something I had no idea was possible. That is pretty neat:

    >>> name = "Eric Idle"
    >>> f"{to_lowercase(name)} is funny."
    'eric idle is funny.'

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I have mixed feelings about code inside f-strings. It seems like a bit of a slippery slope towards losing track of what's happening. I have been tempted to write things like below because I really just need it for the print.

    f"Info print for item  {hex(do_some_parsing(do_some_conversion(value)))}"

Which runs perfectly fine, but at least on my editor syntax highlighting stops working as it is all part of the string. And with that it becomes increasingly hard to work out what is actually being called. Now I resolved myself to pretty much just have one function call and no nesting. Things like f"{str.lower()}" or f"{hex(value)}" are great and I use them a lot.

I don’t think it’ll be an issue. This isn’t exactly new ground. We know the results from other languages. There might be some such abuse, but there’s a lot of other ways to abuse expressions and they don’t happen often because it’s just not worth it.

I have mixed feelings about just grabbing variables inside strings. Prior to this I had a coworker that really liked using the convention:

  "{value}".format(**locals())

I thought it was clever at first, but this made refactoring really hard because you would move around these strings or variables and lose track of what's happening. Maybe IDEs are better at helping with this in recent years?

If I apply a bunch of functions to a variable before printing I tend to use .format() and do it inside the format call, e.g “{}”.format(a.lower().upper())

Something just feels more right about that. Maybe it is the code highlighting that works better.

PyCharm/intellij display the “code” part of f-strings similar to how a variable declaration or function call would be. I’m sure it’s possible for any other editors out there to apply some nicer formatting to f-strings as well.

Swift's string interpolation is usually fine, tbh.

   f"{name.lower()} is funny."

The article demonstrates both methods and functions. I just pasted the function example, but without the showing the function definition itself as it's fairly obvious :-)

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