C++ doesn’t have reflection. As a result, it is impossible to offer a reference to a variable by its name. But as @NicolBolas points out, even if reflection was present, there would be more needed. Not only would it require huge language support (telling the called function what the variables were in the calling scope), … Read more
Overview You can, but only if you write evil code that probably should never end up in production software. So let’s get started! I’m not going to integrate it into your library, but I will show you how to hook into the behavior of f-strings. This is roughly how it’ll work: Write a function that … Read more
An experiment based on your comment, checking what value the object’s __getitem__ method actually receives: class C: def __getitem__(self, index): print(repr(index)) ‘{c[4]}’.format(c=C()) ‘{c[4:6]}’.format(c=C()) ‘{c[anything goes!@#$%^&]}’.format(c=C()) C()[4:6] Output (Try it online!): 4 ‘4:6’ ‘anything goes!@#$%^&’ slice(4, 6, None) So while the 4 gets converted to an int, the 4:6 isn’t converted to slice(4, 6, None) as … Read more
You can use flynt to convert multiple python files to use f-strings. To run it, you need a python 3.6+ interpreter. Then, its as simple as: pip install flynt flynt [relative or absolute path to the root of your project] Keep in mind that it will change files in place, so it is advisable to … Read more
An f-string is syntax, not an object type. You can’t convert an arbitrary string to that syntax, the syntax creates a string object, not the other way around. I’m assuming you want to use user_input as a template, so just use the str.format() method on the user_input object: variable = 42 user_input = “The answer … Read more
f-strings are code. Not just in the safe, “of course a string literal is code” way, but in the dangerous, arbitrary-code-execution way. This is a valid f-string: f”{__import__(‘os’).system(‘install ransomware or something’)}” and it will execute arbitrary shell commands when evaluated. You’re asking how to take a string loaded from a text file and evaluate it … Read more
You can nest expressions to evaluate inside expressions in an f-string. This means you can move the ternary right inside your f-string: string = f’I am {num:{“.2f” if ppl else “”}}’ Note the additional pair of braces needed for nesting. But I don’t think this is cleaner. Personally I find it harder to parse what’s … Read more
I’m afraid that it will be deprecated during the next Python versions Don’t be, str.format does not appear (nor has a reason) to be leaving any time soon, the PEP that introduced fprefixed-strings even states in its Abstract: This PEP does not propose to remove or deprecate any of the existing string formatting mechanisms. Formatted … Read more
It just calls the repr of the value supplied. It’s usage is generally not really needed with f-strings since with them you can just do repr(self.radius) which is arguably more clear in its intent. !r (repr), !s (str) and !a (ascii) were kept around just to ease compatibility with the str.format alternative, you don’t need … Read more
You can’t. Backslashes cannot appear inside the curly braces {}; doing so results in a SyntaxError: >>> f'{\}’ SyntaxError: f-string expression part cannot include a backslash This is specified in the PEP for f-strings: Backslashes may not appear inside the expression portions of f-strings, […] One option is assinging ‘\n’ to a name and then … Read more