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A format specifier begins with a % character. After the percent sign come the following elements, in this order:
An optional argument zero-offset index specifier (that is, the first item has index 0), [index ":"].
An optional left justification indicator, ["-"].
An optional width specifier, [width].
An optional precision specifier, ["." prec].
The conversion type character, type.
The following table summarizes the possible values for type.
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A width specifier sets the minimum field width for a conversion. If the resulting string is shorter than the minimum field width, it is padded with blanks to increase the field width. The default is to right-justify the result by adding blanks in front of the value, but if the format specifier contains a left-justification indicator (an "-" en dash character preceding the width specifier), the result is left-justified by adding blanks after the value.