python 3.12 f-string inelegance

Question

MY_WIDTH = 80
MY_CONSTRUCTED_HDR = f"this is a hdr of length {MY_WIDTH}"
print(MY_CONSTRUCTED_HDR)

this is a hdr of length 80 # YES, but NOT what I need -- see below I want something like this --

                   this is a hdr of length 80

and I miggghht even add another variable or two into the header at some point depending on how gabby the app is

Other constructs I tried --

#MY_CONSTRUCTED_HDR = f"this is a hdr of length {MY_WIDTH} : ^{MY_WIDTH}" # NO prints : ^80

#MY_CONSTRUCTED_HDR = f"{this is a hdr of length {MY_WIDTH}" : ^{MY_WIDTH}} # NO prints : ^80, lots of highlighted syntax errors

#MY_CONSTRUCTED_HDR = f"(this is a hdr of length {MY_WIDTH}" : ^{MY_WIDTH}) # NO prints : ^80, syntax errors

#MY_CONSTRUCTED_HDR = f"{'this is a hdr of length {MY_WIDTH}' : ^{MY_WIDTH}}" # this is CLOSE, prints centered BUT MY_WIDTH in header prints MY_WIDTH, not 80

#MY_CONSTRUCTED_HDR = f"{'this is a hdr of length {MY_WIDTH:2d}' : ^{MY_WIDTH}}" # NO, centers but prints MY_WIDTH:2d

This works but it's two steps:

hdr_string = f"this is a hdr of length {MY_WIDTH}"
MY_CONSTRUCTED_HDR = f"{hdr_string: ^{MY_WIDTH}}" # 
print(MY_CONSTRUCTED_HDR)

Really would like one line of code any ideas? f-strings preferred bc the header text and variables can change radically

I might recommend looking at the formatting of this question/revising it because it is not clear what you are asking about, some of which may be more clear if the formatting was fixed up. Are you trying to right-align something? — Nathaniel Ford
– Nathaniel Ford, Commented Mar 15, 2024 at 0:48
Apparently you want the string to be padded with leading and trailing spaces. Showing it in quotation marks rather than just indented would make that clearer: " this is a hdr of length 80 " (though the line wrapping in this comment doesn't help). — Keith Thompson
– Keith Thompson, Commented Mar 15, 2024 at 1:15

blhsing · Accepted Answer · 2024-03-15 01:11:56Z

1

You can use a nested f-string, with the outer f-string formatting the inner f-string:

MY_WIDTH = 80
print(f"{f"this is a hdr of length {MY_WIDTH}":^{MY_WIDTH}}")

Note that prior to Python 3.12, you cannot use the same quotation mark for an outer f-string, so you would have to do something like:

print(f'{f"this is a hdr of length {MY_WIDTH}":^{MY_WIDTH}}')

edited Mar 15, 2024 at 1:11

answered Mar 15, 2024 at 1:05

blhsing

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1 Comment

doojinsi Over a year ago

weird, but this is the way. thank you blhsing

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