.. meta::
    :description: Formatted strings usage in Python
    :author: Serhii Horodilov sgorodil@gmail.com
    :keywords: python, string, formatting

.. todo: add code examples

###############################
String Formatting: printf-style
###############################

String objects have one unique built-in operation: the ``%`` operator (modulo).
This is also known as the string *formatting* or *interpolation* operator
:cite:`docs-python:printf-formatting`. Given ``format % values`` (where
*format* is a string), ``%`` conversion specifications in *format* are replaced
with zero or more elements of *values*. If *format* requires a single argument,
*values* may be a single non-tuple object.

The conversion flag characters are:

+------------+----------------------------------------------------------------+
| Flag       | Meaning                                                        |
+============+================================================================+
| ``#``      | The value conversion will use the "alternative form"           |
+------------+----------------------------------------------------------------+
| ``0``      | The conversion will be zero padded for numeric values          |
+------------+----------------------------------------------------------------+
| ``'-'``    | The converted value is left adjusted (override the ``'0'`` if  |
|            | both are given)                                                |
+------------+----------------------------------------------------------------+
| ``' '``    | (a space) A blank should be left before a positive number      |
+------------+----------------------------------------------------------------+
| ``'+'``    | A sign character (``'+'`` or ``'-'``) will precede             |
|            | the conversion (overrides a "space" flag)                      |
+------------+----------------------------------------------------------------+

The conversion types are:

+------------+----------------------------------------------------------------+
| Conversion | Meaning                                                        |
+============+================================================================+
| ``'d'``    | Signed integer decimal                                         |
+------------+----------------------------------------------------------------+
| ``'i'``    | Signed integer decimal                                         |
+------------+----------------------------------------------------------------+
| ``'o'``    | Signed octal value                                             |
+------------+----------------------------------------------------------------+
| ``'u'``    | Obsolete type - it is identical to ``'d'``                     |
+------------+----------------------------------------------------------------+
| ``'x'``    | Signed hexadecimal (lowercase)                                 |
+------------+----------------------------------------------------------------+
| ``'X'``    | Signed hexadecimal (uppercase)                                 |
+------------+----------------------------------------------------------------+
| ``'e'``    | Floating point exponential format (lowercase)                  |
+------------+----------------------------------------------------------------+
| ``'E'``    | Floating point exponential format (uppercase)                  |
+------------+----------------------------------------------------------------+
| ``'f'``    | Floating point decimal format                                  |
| ``'F'``    |                                                                |
+------------+----------------------------------------------------------------+
| ``'g'``    | Floating point format. Uses lowercase exponential format if    |
|            | exponent is less that -4 or not less than precision, decimal   |
|            | format otherwise.                                              |
| ``'G'``    |                                                                |
+------------+----------------------------------------------------------------+
| ``'c'``    | Single character (accepts integer or single character string)  |
+------------+----------------------------------------------------------------+
| ``'r'``    | Converts any Python object using ``repr()``                    |
+------------+----------------------------------------------------------------+
| ``'s'``    | Converts any Python object using ``str()``                     |
+------------+----------------------------------------------------------------+
| ``'a'``    | Converts any Python object using ``ascii()``                   |
+------------+----------------------------------------------------------------+
| ``'%'``    | No arguments is converted, results in a ``'%'`` character in   |
|            | the result.                                                    |
+------------+----------------------------------------------------------------+