Step 4: All operators are binary, which means that the first operand is positioned before the operator, and the secondoperand is positioned after the operator.
步骤4：所有的操作符都是二元的，也就是说第一个操作数位于操作符之前，第二个操作符位于操作符之后。
3
The first operand is the format string, which contains one or more format sequences, which specify how the secondoperand is formatted. The result is a string.