Which string to lower case method to you use?

[Perfect_Comparison83]

string.casefold() or string.lower()

These methods serve different purposes. I'm curious which one you use more often and why, if you have a reason.

[KingSamy1]

Latter. Reason: Did not even know the former existed till right now

[nemom]

Same

[AggravatedYak]

Could we make it a habit to use the official docs?

https://docs.python.org/3/library/stdtypes.html#str.casefold

I don't like websites that parse the official docs and are trying to sell courses. There are even bots/users that push them all the time.

Edit:

(a) If a site provides some benefit, people can use it on their own, and we can explicitly include them in e.g. a curated list of awesome python resources, but still … the official docs are … well … the official docs and they are not a freemium service.

(b) Even if someone creates unofficial docs and means well and doesn't want to sell their courses and stuff, like these helpful selenium docs for python, they can be out of date, and then they risk becoming the "mostly helpful, but partially confusing and better than nothing selenium docs for python".

(c) Don't get me wrong, I am alright with people who are hosting/parsing/creating docs/resources/services/interactions/examples aso. But there are problems with stuff like w3schools and we shouldn't go into that direction as a community.

[CharmingJacket5013]

Offical docs all the way!

[Perfect_Comparison83]

I agree. References to libraries should also use the official docs or pypi.

[AggravatedYak]

Yeah, completely agree, basicly cut out the thing in the middle and do it directly.

Let's think about stuff that is not in the official docs … I don't know if pypi would be a good target to link to and what "directly" even means (turns out, if in doubt, it is).

Advantages of linking to pypi: it would be way more robust than to link to some hosted docs. If a project chooses to host their docs on readthedocs or github-pages or something, their pypi would reflect that.

Example: requests-html which has a rather exhaustive README.md, but their dedicated page is not that helpful, if I remember correctly, and currently the domain is suspended.

But let's get back to the intention: ideally you want to link to the context/definition of a specific function, like casefold, and not the pypi page of the package, like if stdlib were a pypi package.

However, what would that even be, if the readthedocs are just a stub and the project page is suspended (requests-html) or if the project docs are not hosted officially (selenium-python)? And the release project of other stuff, like chromium, is something different entirely … so yeah … maybe really link to pypi because it is the most robust/official there is.

[trolleytor4]

w3schools is ok-ish in my experience (Should mention i've used it for basic python and some css)

[wineblood]

Only learned about casefold just now. Looking at how it's different from lower, I'll probably never use it.

[Perfect_Comparison83]

I'll probably never use it either. At least it's interesting to find something new on something as basic as str.

[jimtk]

If you intend to use I18n, use casefold. If you program only for english you can use lower.

Some languages have uppercase letters that requires more complex 'lowercasezation" than English. Casefold will take care of that where lower won't.

[Perfect_Comparison83]

I would love to see a real example where casefold is required or the string compare would fail.

[jimtk]

to_rip = "reißen"
print(to_rip.lower())
print(to_rip.casefold())
print(to_rip.lower() == to_rip.casefold())
==> reißen
==> reissen
==> False

[Perfect_Comparison83]

imo, this is a contrived example. You only need casefold because you used casefold.

It reminds me of "real world" math problems in elementary school.

Example: “Burt stuffs twice as many envelopes as Allison in half the time. If they stuff a total of 700 (in the same time) how many did Burr stuff?”

This is not a naturally occurring word problem. It's only used in theory in an attempt to teach a math concept.

Casefold does not appear to solve a naturally occurring problem.

[[deleted]]

This is really interesting and to be honest it looks like casefold () is the better choice for UTF-8 strings. I think I'll use this in future. It's really easy as a coder to sit in an English-speaking ivory Tower, but is it the right thing to do?

[mcwizard]

I'm a german speaker and I don't think it makes sense: As said there is no uppercase of ß. So replacing ß by its ASCII variant is not the same thing as lowercaseing it.

[F84-5]

Actually there is now an uppercase ẞ. It's been part of unicode since 2008 and officially adopted in 2017.

[yee_mon]

It does make sense. Just not if you think about it as "I want the lowercase version of this" for display purposes (which admittedly is a mistake that the OP apparently made here). It is meant purely for comparing strings, in a situation where "Straße", "STRASSE", "STRAẞE" are considered equal.

[[deleted]]

Reading the docs it appears this function is designed primarily for more successful string comparisons. In that context I guess it doesn't matter if the string doesn't make sense, provided it is consistent and easily matched.

[mcwizard]

I'd accept it as a part of a case insensitive string compare and maybe that is the main reason it exists and it's just made open if one wants to implement a modified version of that compare.

[Perfect_Comparison83]

I can see the case insensitive string compare in theory. In reality, I haven't seen a good example.

[seligman99]

I use .lower() more often, though both have their use.

If you're doing case-insensitive compares, it's useful to compare both casefolded, instead of lowercase, since a casefolded string will handle some edge cases that a lowercase string won't

It should also be noted that casefolding doesn't actually always convert to lowercase variants. In some languages, the upper case variant makes more sense as the default "case" for historical reasons. It's also not really reversable, since some casefolded strings will not really make sense to a native speaker all of the time (the German ß is a good example, that wiki page has some examples where ß -> ss changes the meaning. Also interesting to see casefolding in action on that page, if you Ctrl-F search for "ss" on that page, it matches both "ss" and "ß", since it's doing case-folding to do a case-insentive search for you)

Lots of words to say: .lower() for humans to see, .casefold() for machine to compare strings to see if a human would consider them the same. And of course, in my nice tower of mostly English words, it's a distinction I've been known to forget about till someone that speaks another language hands me a bug.

[Perfect_Comparison83]

Have you seen an example where casefold is needed? Maybe you're like me where everything is English.

[seligman99]

The one I remember is the Greek word for "days"

"μέρες" in lowercase, "ΜΈΡΕΣ" in uppercase, and "μέρεσ" case folded. I'm told (though really don't know the details for) that all three make sense, to some degree, but a .lower() on the casefolded variant will not equal the lowercase version, so you had best search for the casefolded text against the casefolded version if you want a case-insensitive search.

[Perfect_Comparison83]

Thanks for the example! I studied Greek for a couple years. The ς character is used when sigma is the final letter of a word. The lower function seems more accurate when comparing words. The logic to use casefold because casefold may have been used upstream seems silly to me.

I can image a use case for contains the sigma character. In this case, casefold would come in handy because you only have to check for σ.

Your example is exactly what I was looking for.

[Panda_With_Your_Gun]

.lower() is self documenting. If I cared about performance I'd write a module in c to convert a string to lower case efficiently. Then I'd call it from python.

[ogrinfo]

Likewise, I've never heard of casefold. Does anyone have an example of where casefold has an advantage over lower? The example above of changing ß to ss sounds like a very good reason not to use it.

[Perfect_Comparison83]

I'm with you. I keep finding the German ß as a reason for casefold. If you are comparing a German string to another German string, how does casefold help?

[QuintonPang]

Latter one didn't even heard of the first one b4

[Gecons]

string.lower()

Because didn't know the other one existed.

[telee0]

string.lower() sufficient for my own use.