How to format a floating number to fixed width in Python

Question

How do I format a floating number to a fixed width with the following requirements:

1. Leading zero if n < 1
2. Add trailing decimal zero(s) to fill up fixed width
3. Truncate decimal digits past fixed width
4. Align all decimal points

For example:

% formatter something like '{:06}'
numbers = [23.23, 0.123334987, 1, 4.223, 9887.2]

for number in numbers:
    print formatter.format(number)

The output would be like

  23.2300
   0.1233
   1.0000
   4.2230
9887.2000

Answer 1

for x in numbers:
    print "{:10.4f}".format(x)

prints

   23.2300
    0.1233
    1.0000
    4.2230
 9887.2000

The format specifier inside the curly braces follows the Python format string syntax. Specifically, in this case, it consists of the following parts:

• The empty string before the colon means "take the next provided argument to format()" – in this case the x as the only argument.
• The 10.4f part after the colon is the format specification.
• The f denotes fixed-point notation.
• The 10 is the total width of the field being printed, lefted-padded by spaces.
• The 4 is the number of digits after the decimal point.