Python in a Nutshell, 2nd Edition

String Formatting

In Python, a string-formatting expression has the syntax:

format % values

where format is a plain or Unicode string containing format specifiers and values is any single object or a collection of objects in a tuple or dictionary. Python’s string-formatting operator has roughly the same set of features as the C language’s printf and operates in a similar way. Each format specifier is a substring of format that starts with a percent sign (%) and ends with one of the conversion characters shown in Table 9-1.

Table 9-1. String-formatting conversion characters

Character	Output format	Notes
d, i	Signed decimal integer	Value must be number.
u	Unsigned decimal integer	Value must be number.
o	Unsigned octal integer	Value must be number.
x	Unsigned hexadecimal integer (lowercase letters)	Value must be number.
X	Unsigned hexadecimal integer (uppercase letters)	Value must be number.
e	Floating-point value in exponential form (lowercase e for exponent)	Value must be number.
E	Floating-point value in exponential form (uppercase E for exponent)	Value must be number.
f, F	Floating-point value in decimal form	Value must be number.
g, G	Like e or E when exp is >=4 or < precision; otherwise, like f or F	exp is the exponent of the number being converted.
c	Single character	Value can be integer or single-character string.
r	String	Converts any value with repr.
s	String	Converts any value with str.
%	Literal % character	Consumes no value.

Between the % and the conversion character, you can specify a number of optional modifiers, ...