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For f format, the flag character '-', means that
the output should be left justified within the
field. The default is to pad with blanks on the
left. '+' character means that the conversion
will always begin with a sign (+ or -). The
blank flag character means that a non-negative
input will be preceded with a blank. If both
a '+' and a ' ' are specified, the blank flag
is ignored. The '0' flag character implies that
padding to the field width will be done with
zeros instead of blanks.
The field width is treated as the minimum number
of characters to be printed. The default is to
add no padding. Padding is with blanks by
default.
The precision, if set, is the number of digits
to appear after the radix character. Padding is
with trailing 0s.