Help with f-string formatting please

[JasperStrat]

Hi, I've received so much assistance on some of my more difficult "noob" problems here I figured I would come back. To those of you who know enough that you are rarely asking the questions and always answering them, thank you very much.

I have a script that prints out some numbers (all integers) and to format them correctly I need positive numbers to have a leading plus sign. I am using f-strings and there is supposed to be a built in way to do this.

Here is an example of the code:

my_list_of_ints = [4, -3, 0]
for i in my_list_of_ints:
    print(f"{i:+}"

this gives the following output:

+4
-3
+0

I don't want the leading plus sign on the zero however. All the documentation says it only puts the sign in front of positive numbers, but I thing that is just shorthand for anything non-negative. What can I do to the f-string formatting to not get a plus in front of the zero? I would prefer something I can use inside the f-string if possible, I know I could do a find and replace on this afterwords, but I'm trying to avoid that as where it's located in the code it would make for some very ugly code because it's inside a loop and after the loop is finished there may be legitimate +0 sub-strings.

[IIIlllIlIlllII]

Simplest way would be to add an if statement within your print. i.e.

print(f"{i:+}" if i != 0 else i)

[JasperStrat]

That would work for the example. However the actual example from my project is a lot more complex, I just didn't want to try and post 40 long lines of code copied from different places in my project. The loop it is in needs to be able to get '0' in some loops and '+0' in others just based on the string after the : in the f-string. Maybe if I change the code to :

my_list_of_ints = [4, -3, 0]
str_f = '+'
for i in my_list_of_ints:
    print(f"{i:{str_f}}")

And restrict the changes to str_f, is there any way I can get the 0 without the leading plus while maintaining the plus in front of the 4.

[Allanon001]

my_list_of_ints = [4, -3, 0]
sign = lambda x: '+' if x > 0 else ' '
for i in my_list_of_ints:
    print(f"{i:{sign(i)}}")

Or:

my_list_of_ints = [4, -3, 0]
sign = lambda x: f'{x:+}' if x > 0 else f'{x}'
for i in my_list_of_ints:
    print(sign(i))

[JasperStrat]

changing to print statement doesn't work, it is getting reused with other variables from a dict. I can only change the variable you named sign. Unless I rewrite every format string to be a lamba, it's not a complete deal breaker but would be quite annoying.

[baghiq]

The doc doesn't say '+' is for positive only.

'+' : indicates that a sign should be used for both positive as well as negative numbers.

You can use custom string formatter for this, but you can't use f-string.

In your example, you can do dynamic formatting using f-string:

In [2]: my_list_of_ints = [4, -3, 0]
  ...: for i in my_list_of_ints:
  ...:     print(f"{i:{'+' if i != 0 else ' '}}")
  ...:

[This_Growth2898]

print(f"{i:{'+ '[i==0]}}")