strFormatting

Python String formatting

F-strings

Prefer f-strings where possible. They are easy to read and often provide performance benefits.

.format()

Variable referencing

Implicit referencing

At {} the given variable will be inserted.

"Hello {}!, I haven't seen you for {} days.".format("Joe", 5)

Positional referencing

You can provide the argument number (starting by 0).

"Hello {1}!, I haven't seen you for {2} days.".format("unused string", "Joe", 5)

Keyword referencing

References by name are also possible

"Hello {name}!, I haven't seen you for {time} days.".format(name="Joe", time=5)

Formatting

Referencing and formattin gis separated by a colon (:): e.g. {name:d}, {:d}, {1:d}, ...

Alignment

Only the remaining space is considered for alignment.

Option	Description
<	left aligned
^	centered
>	right aligned
=	signed; left aligned

Numbers

General options

Option	Description
d	dec
c	unicode char
b	bin
o	oct
x / X	hex
e / E	exp notation
f / F	Float (default=6, F: inf -> INF; nan -> NAN)
g	"general"; rounds to significant digits (default=6)
G	Same as g; auto-switches to 'E' if useful
%	percentage

All upper case options return the corresponding upper case output.

Padding/width (int & float); sign

If the number would not be displayable the relevant formatting options get ignored.

• {:<pad>.<decimal-places>f} e.g. "{:2.2f}".format(2.3456) results in 2.34
• {:<pad>.<decimal-places>f} e.g. "{:2.2f}".format(2.3456) results in 2.34 (note the padding with spaces)
• {:<pad>.<decimal-places>f} e.g. "{:02f}".format(2.3456) results in 02 (note the padding with zeros)
• {:+f} e.g. "{:+f}".format(2.3456) -> +2 (note the padding with zeros)
  • + shows + and -
  • - shows only -
  • (space) shows a padding space (in case of +) otherwise -

For strings <decimal-places> can be seen as truncating the string

Some more complex examples:

• "{:^8.2f}".format(-34.6841)) results in -34.68
• "{:*^-18.2f}".format(-34.6841) results in ******-34.68******