Example of using [0][width] in format specifier

Question

I have the following format string:

>>> '{num:+,.4f}'.format(num=-200000)

This uses the:

• [sign]
• [grouping_option]
• [.precision]
• [type]

Options in the format specifier defined here.

The format spec is defined as:

format_spec     ::=  [[fill]align][sign][#] here ==> [0][width]<== here [grouping_option][.precision][type]

What would be an example of the [0] and [width] options? What are those used for?

Answer 1

The Width means pad the entire number on the left so that it produces at least that many characters, useful when the numbers need to line up. The 0 means pad the width with zeros instead of spaces.

>>> '{num:+20,.4f}'.format(num=-200000)
'       -200,000.0000'
>>> '{num:+020,.4f}'.format(num=-200000)
'-00,000,200,000.0000'