string-formatting

I want to achieve the following with str.format : x,y = 1234,5678 print str(x)[2:] + str(y)[:2] The only way I was able to do it was: print '{0}{1}'.format(str(x)[2:],str(y)[:2]) Now, this an example and what I really have is a long and messy string, and so I want to put slicing inside the {} . I've studied the docs , but I can't figure out the correct syntax. My question is: is it possible to slice strings inside a replacement field? Martijn Pieters No, you cannot apply slicing to strings inside a the replacement field. You'll need to refer to the Format Specification Mini-Language ; it

Using format! , I can create a String from a format string, but what if I already have a String that I'd like to append to? I would like to avoid allocating the second string just to copy it and throw away the allocation. let s = "hello ".to_string(); append!(s, "{}", 5); // Doesn't exist A close equivalent in C/C++ would be snprintf . I see now that String implements Write , so we can just use write! : use std::fmt::Write; pub fn main() { let mut a = "hello ".to_string(); write!(&mut a, "{}", 5).unwrap(); println!("{}", a); assert_eq!("hello 5", a); } ( Playground ) It is impossible for this

public class Divers { public static void main(String args[]){ String format = "|%1$-10s|%2$-10s|%3$-20s|\n"; System.out.format(format, "FirstName", "Init.", "LastName"); System.out.format(format, "Real", "", "Gagnon"); System.out.format(format, "John", "D", "Doe"); String ex[] = { "John", "F.", "Kennedy" }; System.out.format(String.format(format, (Object[])ex)); } } output: |FirstName |Init. |LastName | |Real | |Gagnon | |John |D |Doe | |John |F. |Kennedy | I want the output to be centered. If I do not use '-' flag the output will be aligned to the right. I did not find a flag to center text

I've read through a good chunk of Expert F# and am working on building an actual application. While debugging, I've grown accustomed to passing fsi commands like this to make things legible in the repl window: fsi.AddPrinter(fun (x : myType) -> myType.ToString()) I would like to extend this to work with the printf formatter, so I could type e.g. printf "%A" instanceOfMyType and control the output for a custom type. The book implies that this can be done (p 93, "Generic structural formatting can be extended to work with any user-defined data types, a topic covered on the F# website"), but I

I've run into a fairly simple issue that I can't come up with an elegant solution for. I'm creating a string using str.format in a function that is passed in a dict of substitutions to use for the format. I want to create the string and format it with the values if they're passed and leave them blank otherwise. Ex kwargs = {"name": "mark"} "My name is {name} and I'm really {adjective}.".format(**kwargs) should return "My name is mark and I'm really ." instead of throwing a KeyError (Which is what would happen if we don't do anything). Embarrassingly, I can't even come up with an inelegant

Sorry if this question was made already, I've made a deep search and nothing. Now, I know that: String.format("%05d", price); Will be padding my price with zeros to the left, so a price of 25 will result in 00025 What if I want to pad them to the right, so the result is 25000 ? How do I do that using only String.format patterns? Reimeus You could use: String.format("%-5s", price ).replace(' ', '0') Can I do this using only the format pattern? String.format uses Formatter.justify just like the String.printf method. From this post you will see that the output space is hard-coded, so using the

Thanks to David Beazley's tweet , I've recently found out that the new Python 3.6 f-strings can also be nested: >>> price = 478.23 >>> f"{f'${price:0.2f}':*>20s}" '*************$478.23' Or: >>> x = 42 >>> f'''-{f"""*{f"+{f'.{x}.'}+"}*"""}-''' '-*+.42.+*-' While I am surprised that this is possible, I am missing on how practical is that, when would nesting f-strings be useful? What use cases can this cover? Note: The PEP itself does not mention nesting f-strings, but there is a specific test case . I don't think formatted string literals allowing nesting (by nesting, I take it to mean f'{f".."}