Capitalize Sentences |2|
~~~~~~~~~~~~~~~~~~~~~~~~

Write a function named *capitalize_sentences* which takes a string
including multiple sentences and returns a string where the first letter
of each sentence in the original string is converted to uppercase to
correct the typos.

A sentence may end with the following characters: ``'.'``, ``'?'``,
``'!'``. Your function should not interfere with other parts of the
string.

You may assume that there will be a single blank character between each
sentence. You must preserve this blank character in the recovered
string. There will be no blank characters after the last sentence.

.. container:: sampleio

   Sample I/O:

.. |2| image:: ../../figures/difficulty_four.png
   :class: difficulty

.. code:: default

   >>> capitalize_sentences('lorem. ipsum? dolor sit amet, consectetur! adipiscing elit.')
   'Lorem. Ipsum? Dolor sit amet, consectetur! Adipiscing elit.'

   >>> capitalize_sentences('string methods are really useful in Python! you need to know them to succeed in CENG240.')
   'String methods are really useful in Python! You need to know them to succeed in CENG240.'

.. raw:: html

   <button type="button" class="collapsible" onclick="toggle()">

Show the Answer

.. raw:: html

   </button>

.. raw:: html

   <div class="hiddenanswer">

.. code:: python

   def capitalize_sentences(string):
       def upper_initial(string):
           return string[0].upper() + string[1:] if string else string

       def split_by_and_capitalize(string, delimiter):
           sentences = [sentence.lstrip() for sentence in string.split(delimiter)]
           return (delimiter + ' ').join(
                   [upper_initial(sentence) for sentence in sentences])

       delimiters = ['.', '?', '!']
       for delimiter in delimiters:
           string = split_by_and_capitalize(string, delimiter)
       return string.rstrip() # discard trailing whitespace

.. raw:: html

   </div>