Python 3.6 introduced a new way to format strings, called Formatted string literals, or just f-strings. Everyone on the internet seem to be happy about it. I'm definitely not.

For starters, Python 3 already had 3 built-in ways of doing it before. Just think about it... 3 ways to format strings in language that declares simplicity as a goal:

There should be one-- and preferably only one --obvious way to do it. - The Zen of Python

These methods are:

  • Using % (modulo) operator (old way, supported in logging module)
  • Using .format() string method (relatively new way)
  • Using template strings (very old and quite slow way)

And I'm not even talking about basic string concatenation.

And as this is clearly not enough for simplicity, they've just added another method. It works almost like .format():

>>> foo = "bar"
>>> f"f-strings allows me to use {foo.upper()} just like this"
"f-strings allows me to use BAR just like this"

The idea is to directly use names from current scope for formatting.

So now we have 4 ways to format strings, all of which can be mixed up. I'm already sick of seeing all kind of mistakes like using {} with modulo formatting, or %s with .format() formatting, mixing both methods in the same file. And as programmers do mostly read the code, I do care about it's comprehensiveness and readability.

Another concern is tooling support. Python is already looking bad from this point of view, having just pylint as a standalone linter (sorry, but pyflakes is a joke compared to it). PyCharm is brilliant without any doubts, but it's not everyone cup of tea. And while even pyflakes can handle checking for usage of uninitialized variable, doing the same with f-strings is more complicated, and is not supported for now AFAIK.

Returning to Python from Go land, all of this really bothers me. While Go devs are thinking about Simplicity Debt, Python folks just keep adding features.

And while I'm quite happy with Python 3 Type Hints, because it actually helps to understand the code by clearly indicating argument types, I'm absolutely not happy with f-strings, especially seeing how they are already breaking linters and cutting off Python 2 compatibility at work.


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