What do you use to format a string,%, or format?

The % operator is a binary operator, so it will always receive two parameters. The first one is already reserved for the string that will be formatted, so the language is limited to passing all the values of the format through the second parameter;

This has some implications:

• The parameter that has the formatting values will necessarily be a composite type, as it must have the ability to store multiple values;

  >>> string % parameters
  

• It is limited to always using only positional parameters, when passing them through a tuple, or named parameters, when passing them through a dictionary, but never both concurrently;

  >>> '%s %s' % ('john', 'doe')  # posicional
  john doe
  
  >>> '%(first)s %(last)s' % {'first': 'john', 'last': 'doe'}  # nomeado
  john doe
  

• >>> 5 % 2  # Calcula o resto da divisão
  1
  
  >>> string % parameters  # Formata string????
  

You can not use language tools such as tuple deconstructing or dict deconstructing to ease the passing of values;

>>> name = ['john', 'doe']
>>> '%s %s' % (*name)
SyntaxError: invalid syntax

Use positional parameters, but use them in random order;

>>> '{1}, {0}'.format('john', 'doe')
doe, john

Define spacing in the string by replacing the character to be displayed: in the old style, a blank is always displayed;

>>> '{:_<10}'.format('john')
john______

Centralize content with reference to available space;

>>> '{:_^10}'.format('john')
+++john+++

By using flagged numbers, you can control the position of the signal;

>>> '{:=5d}'.format(-3)
-   3
>>> '{:=+5d}'.format(3)
+   3

The format method accepts named parameters to define the values, not depending more on dictionaries or tuples;

>>> '{first} {last}'.format(first='john', last='doe')
john doe

>>> name = ('john', 'doe')
>>> '{0} {1}'.format(*name)
john doe

>>> name = {'first': 'john', 'last': 'doe'}
>>> '{first} {last}'.format(**name)
john doe

You can access values directly from string ;

>>> john = {'first': 'john', 'last': 'doe'}
>>> '{name[first]} {name[last]}'.format(name=john)
john doe

Similarly, you can access object attributes;

>>> 'Nome do arquivo: {0.name}'.format(open('arquivo.txt'))
Nome do arquivo: arquivo.txt

It is possible for objects to take control of their own formatting, just as with the object datetime.datetime ;

>>> from datetime import datetime
>>> '{:%Y-%m-%d %H:%M}'.format(datetime.now())
2017-12-11 20:52

This is possible because the format method will search for the __format__ method of the object;

You can parameterize the format itself with its values;

>>> '{:_{align}{width}}'.format('john', align='^', width='10')
___john___
>>> '{:_{align}{width}}'.format('john', align='>', width='10')
______john