How to format a float with a comma as decimal separator in an f-string?
Solution 1
If you want to format floats with a comma within the f-string, you can either use replace after casting the float to a string:
position = 123.456
f"Position\t{str(position).replace('.',',')}"
A second option is to use the Python standard library module locale (but it is not thread-safe):
import locale
locale.setlocale(locale.LC_ALL, 'nl_NL')
f"Position\t{locale.format('%.3f', position)}"
A third option is to use the library babel (preferred in case of library routines):
from babel.numbers import format_decimal
f"Position\t{format_decimal(position, locale='nl_NL')}"
All three options return the same result for the given example:
'Position\t123,456'
Solution 2
As @michel-de-ruiter mentioned, the f
format does not work with locale. On the other hand, you can't set the precision using n
format. For example, if you want 4 digits after decimal separator:
import locale
locale.setlocale(locale.LC_ALL, 'nl_NL')
position = 123.45678999
print(f'{position:.4n}') # output: 123,4 (not quite what we wanted!)
However, you can round the number with the desired precision before formatting it:
print(f'{round(position, 4):n}') # output: 123,4567 (that's it!)
Solution 3
If the g
format is good enough for you, use n
instead:
resultfile.write(f"Position\t{position:.7n}")
While n
works (uses the current locale setting when used) instead of both d
and g
, there is no such thing for the f
format unfortunately...
Related videos on Youtube
Comments
-
seaver over 1 year
For some machine control in python, I write the results to a text-file, that someone else can copy into Excel (this is the most convenient way in this situation). However, in the Netherlands, Excel has a comma as decimal separator and thus I want to have the result "position" in the text-file as 123,456, but when I use the f-string method like this:
resultfile.write(f"Position\t{position:.5}")
This will obviously result in a dot decimal separator.
How can I change this to a comma without iterating through the whole file int the end and replace the dots with commas?
-
Arne over 4 yearsAn fstring is just a string, so
f"Position\t{position:.5}".replace('.', ',')
should work just fine, right? -
Arne over 4 yearsAlso: stackoverflow.com/a/6633912/962190 This answer talks about a different issue (printing number with comma separation every three decimal positions), but the locale setting might influence your format as well.
-
-
marcelm about 3 yearsThis changes the thousands separator to
,
but the question is asking about the decimal separator. It doesn't answer the question at all. -
Michel de Ruiter almost 3 years@seaver This does not answer the question. All this does is introducing a thousands separator (
,
). It does not change the decimal separator (stays.
).