❓Are you using f-strings to format your strings in Python? Yes? Great.
🚀 If not, consider dropping your tired old format approach and get with the new(ish) stuff: f-strings.
📚 There's plenty of blogs out there that tell you all about f-strings. They tell you at length about the old approaches, % formatting and .format(), so I'm not going to go over all that, I'm just here to encourage you to take a look at f-strings.
🤔 Why? I'm using f-strings all the time now, and .format() seems clunky and overly verbose in comparison.
Here's the basics:
- f-strings is the name given to 'formatted string literals'
- Python 3.6+
- Similar in approach to .format() but less verbose, which helps keep your line length down and improve code readability.
A few examples
Here's a simple combination of string variable declaration and print using .format():
>>> device = "clocks"
>>> time = "thirteen"
>>> sentence = "The {} were striking {}".format(device, time)
>>> print(sentence)
The clocks were striking thirteen
Now, the same code, but using f-string:
>>> device = "clocks"
>>> time = "thirteen"
>>> sentence = f"The {device} were striking {time}"
>>> print(sentence)
The clocks were striking thirteen
Looking at the two approaches it doesn't seem like much of a difference. But I think the improvement are enough to make me switch to f-strings and never look back.
- F-strings save you eight characters by using a single 'f' to declare that the code uses f-strings, rather than the '.format()'.
- Writing code is more intuitive, I feel, adding the string variables within the string itself, rather than saving this for the end of the line.
- Reading code is easier because the declarations are right there in the string, again, rather than at the end of the line.
- N.B. .format does allow variables in the braces, but that has the additional requirement of having to declare those in the final brackets, like so:
sentence = "The {device} were striking {time}".format(
device=device, time=time
)
As you can see, this approach is even more verbose.
In isolation, all this points may seem minor, but as string formatting is such a necessary part of so much Python code, these small improvements can make a big difference to the overall experience of reading and writing Python.
Some extra details
Quotation marks can be used within an f-string, as long as different types are used
>>> f'{"quoted string"}'
'quoted string'
Methods can be called directly
>>> sentence = f"The {device.upper()} were striking {time}"
>>> print(sentence)
The CLOCKS were striking thirteen
For more details, check out PEP 498, the proposal that was developed into f-strings here.
Give f-strings a go, I hope you find them as useful as I have.
Thanks for reading.
Latest comments (7)
I personally enjoy f-strings when using them to write formatted input files for different scientific analysis software.
Some softwares require input files with a specified column format, and others do not.
Having the ability to take an example input file, changing each parameter to an f-string that calls a variable stored in a dictionary in another file is very useful (especially for reproducibility in my case).
To be honest, I like f strings because:
But I guess that if you want more uses then you can use formats
Good summary. I'm thinking along the same lines.
F strings are fantastic but format absolutely still has its uses. Named format placeholders allow dictionary expansion to dynamic arguments, for one, not to mention string formatting, alignment, etc. I agree for short concise strings, they’re excellent!
Good points, I didn't think about the alignment aspect as I was writing this. Thanks for the reminder.
f-strings are one of my absolute favorite things in Python lol, gotta love expressive and concise code
true lol