Python string literals are kinda funny

Python string literals are kinda funny(sebsite.pw)

38 points by jandeboevrie 2 days ago | 17 comments

PyWoody 1 hour ago |

Whenever I read people's takes about Python on HN, I always feel like I'm using an entirely different language.

dwdz 2 hours ago |

I'm not a fan of f-strings.

I feel like 90% of new Python features in the last 10 years just increased language complexity without any benefit.

ForceBru 1 hour ago | |

I'm a HUGE fan of f-strings and I think they should be added to more or less every language in existence. (This is just to show how much I like f-strings, not to be taken literally) `printf`-style format strings seem outdated: why use format strings when I can put my variables IN THE STRING? I want the result of `x+y` to be put {HERE} in this string. Well, just write `"This is here: {x+y} blah"` — it makes perfect sense and immediately lets me see what the resulting strings generally look like.

Basic usage is a no-brainer: write your string, put variables or short expressions in curly braces, add `printf`-style format specifiers after the colon. This is also great because it's a natural extension of `printf`-style format strings.

Of course you can write complicated and confusing f-strings. But then you can write complicated and confusing... anything, really. Many programming languages have extremely weird quirks and cases where basic syntax can be transformed into an unreadable monstrosity, like C syntax for pointers to functions and arrays.

Sure, this increases the language's complexity, but you don't have to use all of it to reap the benefits.

layer8 7 minutes ago | | |

> why use format strings

Because these are used for locale-specific configuration data. `"This is here: {x+y} blah"` on the other hand isn’t a string (mere data), it’s a program, because you can have arbitrary expressions inside the braces. You don’t want to repeat the `x+y` in each localization file.

I have nothing against ergonomic program constructs for composing strings, but please let’s not confuse such program constructs with mere string literals.

Izkata 30 minutes ago | | |

Those aren't the only two options. Like GP I don't like f-strings, but there was something introduced before that: the format function.

  "The thing is {foo}, and also {foo} again".format(foo=x+y)

It also supports positional with empty {}. And like f-strings, you can put formatting information after a colon.

%-based printf-style did also have named variables like this but it seemed less known.

vova_hn2 15 minutes ago | |

I like f-strings but I don't like that there are at least five ways to format stings.

1. %-formatting [1]

2. str.format [2]

3. string.Template [3]

4. f-string [4]

5. t-string [5]

What happened to "one-- and preferably only one --obvious way to do it"? [6]

Also, the way string formatting interacts with logging is a total mess. People just pass f-strings to logging, which seems to be an intuitive way to do it. Except it limits your options if you want to collect structured logs and it doesn't allow you to use late evaluation based on log level.

[1] https://docs.python.org/3/library/string.html#format-example...

[2] https://docs.python.org/3/library/stdtypes.html#str.format

[3] https://docs.python.org/3/library/string.html#string.Templat...

[4] https://docs.python.org/3/reference/lexical_analysis.html#f-...

[5] https://docs.python.org/3/reference/lexical_analysis.html#t-...

[6] https://peps.python.org/pep-0020/

bulatb 1 minute ago | | |

When Python <3.4 was still maintained alongside Python 2.7, it wasn't even obvious which Python should have one obvious way to do it.

gucci-on-fleek 10 minutes ago | | |

> What happened to "one-- and preferably only one --obvious way to do it"?

There arguably still is—just use f-strings for everything, unless you need to support ancient Python, in which case use %-formatting.

t-strings are a special case, but in theory most functions should only accept regular strings or templates, so there should only be one choice there too.

> Also, the way string formatting interacts with logging is a total mess [...] it doesn't allow you to use late evaluation based on log level.

This all seems to be a side-effect of the fact that string formatting produces static strings, so I don't think that there's much that can be done here (but maybe t-strings can be creatively used here somehow).

ajrouvoet 1 hour ago | |

It is baffling to me that Python seems to insist on reinventing language features and coming up with the most incomprehensible of designs. The whole dataclass and serialisation ecosystem comes to mind, as well as the evolution of typing.

The language exposes so much of its internals that even if the design were consistent, the ecosystem of (buggy) libs and tools makes it inconsistent.

LPisGood 1 hour ago | | |

PKL files and the entire multiprocessing paradigm is one of the worst experiences I’ve ever had with a programming language feature. Surely there has to be a better way.

analog31 2 hours ago | |

Indeed, and I get that one can ignore those features (I do), but finding them in existing code or having the AI coding agent use them diminishes the "easy for beginners" aspect.

ForceBru 16 minutes ago | | |

How is, say, `age = 5; print(f"Age: {age} years old")` not easy for beginners? IMO it's as easy as it gets: you want the value of `age` printed {HERE}, so you just put it where you want it, surrounded by curly brackets.

orf 1 hour ago | | |

Are f-strings not easy for beginners? What would you prefer instead?

phyzome 1 hour ago |

Goofy edge cases aside, I think f-strings are great.

xg15 2 days ago |

here's a valid f-string:

>>> f'{'}'}' '}'

Huh? I remember learning the rule that you can't nest quotes inside fstrings if they are the same kind (unlike in bash) - e.g

  f"{mydict["foo"]}"

would be a syntax error, but

  f"{mydict['foo']}"

  f'{mydict["foo"]}'

would be valid.

The reason being the same like for the rstring weirdness: The lexer comes first and identifies the string literal, then for fstrings, the python parser is invoked again for each {...} expression to parse it.

This is unlike other nested expressions, which are already split up by the lexer and then parsed in one go.

Did that change at some point?

xg15 2 days ago | |

Update: They really changed it! (in python 3.12)

There was a PEP about it:

https://stackoverflow.com/questions/78388333/nested-quotes-i...

https://docs.python.org/3.12/whatsnew/3.12.html#pep-701-synt...

globular-toast 44 minutes ago | | |

Wow, I didn't know this either. I find it a bit crazy. It must make no sense without syntax highlighting. But I suppose who writes code without highlighting any more?

madprops 1 hour ago |

Great new way to write blog posts!

cocodill 1 hour ago |

do not get the funny part of the pythons string.

TZubiri 1 hour ago |

Been using python for almost 10 years. I never use any of the funky strings.

Instead of reading like 10 PEPs for f strings, I just use the + operator on strings and backslash escaping, big whoop.

PyWoody 1 hour ago | |

Instead of 10 PEPs, you could read one helpful cheatsheet: https://www.pythonmorsels.com/string-formatting/#cheat-sheet....

andai 1 hour ago | |

age = 32

print(f"Age: {age}")

Thus concludes the lecture on f-strings.

kzrdude 21 minutes ago | | |

I find it funny and satisfying that Python has converged to it's own "printf", by which I mean print(f"").

smohare 1 hour ago | |

Right, because x + " " + y is more clear than of simply f"{x} {y}".

Been using python for longer than 10 years and immediately started using f-strings when I could. It takes almost no time to understand the basics.

smitty1e 2 hours ago |

Whenever I'm building a JSON document, I revert to the old %s syntax just because it's more tidy than an f-string.

folkrav 2 hours ago | |

Am I understanding that you’re building JSON with string interpolation? If so any special reason you wouldn’t build a dict and json.dumps() it?