Formatting numbers (aligning digits and decimal places)

This lesson covers formatting numbers in Julia, with the aim of displaying them in a readable form.

Loading the standard Printf module with using Printf gives you @printf("%.2f", value) to fix the number of decimal places and @printf("%03d", value) to pad the front with zeros. Both are handy for displaying amounts and for building numbered file names.

The sample code turns 1234.5 into two-decimal form with @printf("%.2f ", price) and 7 into the zero-padded "007" with @printf("%03d ", num). Note that these are macros.

A common early stumble is forgetting the using Printf import. Unlike most features, formatted output needs the Printf module loaded explicitly.

In professional work, results displayed raw have inconsistent widths and read badly, so this kind of formatting just before display is standard.