List comprehensions
===================


Fibonacci sequence v1
---------------------

.. interactive_code_block:: 
   :caption: Shortest version

   def fibonacci(length):    # write Fibonacci series up to n
       a, b = 0, 1
       for i in range(length):
           print(a, end=' ')
           a, b = b, a + b

   fibonacci(15)

   
.. interactive_code_block:: 
   :caption: !!!

   def fibonacci(length):
       sequence = []
       for number in range(0, length):
           if len(sequence) < 2:
               sequence.append(number)
           else:
               sequence.append(sequence[-2] + sequence[-1])
       return sequence

   print(fibonacci(15))


.. interactive_code_block:: 
   :caption: !!!

   length= 15
   sequence = []
   [sequence.append(number) if len(sequence) < 2 else sequence.append(sequence[-2] + sequence[-1]) for number in list(range(0, length))]
   print(sequence)


.. interactive_code_block:: 
   :caption: !!!

   l = 15
   s = []
   [s.append(n) if len(s) < 2 else s.append(s[-2] + s[-1]) for n in list(range(0, l))]
   print(s)


Fibonacci sequence v2 (Binet formula)
-------------------------------------

.. interactive_code_block:: 
   :caption: !!!

   square_root_of_5 = 5**0.5
   phi = (1 + square_root_of_5) / 2
   
   def fibonacci_number(index):
       return int((phi**index - (1 - phi)**index) / square_root_of_5)

   fibonacci_sequence = [fibonacci_number(index) for index in range(0, 15)]
   print(fibonacci_sequence)


.. interactive_code_block:: 
   :caption: !!!

   square_root_of_5 = 5**0.5
   phi = (1 + square_root_of_5) / 2
   
   sequence = [int((phi**n - (1 - phi)**n) / square_root_of_5) for n in range(0, 15)]
   print(sequence)


Months with an 'r'
------------------

.. interactive_code_block::
   :caption: Only eat oysters in months with an 'r'

   months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
   
   months_without_r = [month for month in months if 'r' not in month]
   print('Don\\'t eat oysters between {} and {}.'.format(months_without_r[0], months_without_r[-1]))


Abbreviated name
----------------

.. interactive_code_block::
   :caption: Only eat oysters in months with an 'r'

   weekdays = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
   
   abbreviated_weekdays = [weekday[:3] for weekday in weekdays]
   print(abbreviated_weekdays)


Abbreviated name 2
------------------

.. interactive_code_block::
   :caption: Only eat oysters in months with an 'r'

   term = 'Light Amplification by Stimulated Emission of Radiation'
   
   abbreviated_term = [character for character in term if character.isupper()]
   print(''.join(abbreviated_term))


List of leap years
------------------

.. interactive_code_block::
   :caption: Generate a list of leap years using a for loop

   # Definition of a leap year from:
   # https://github.com/python/cpython/blob/3.9/Lib/calendar.py#L100
   def isleap(year):
       """Return True for leap years, False for non-leap years."""
       return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)
   
   leap_years = []
   for year in range(1895, 1916):
       if isleap(year):
           leap_years.append(year)
   
   print(leap_years)


.. interactive_code_block::
   :caption: Generate a list of leap years using a list comprehension

   # Definition of a leap year from:
   # https://github.com/python/cpython/blob/3.9/Lib/calendar.py#L100
   def isleap(year):
       """Return True for leap years, False for non-leap years."""
       return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)
   
   leap_years = [year for year in range(1895, 1915) if isleap(year)]
   print(leap_years)


.. interactive_code_block::
   :caption: Generate a list of leap years using a list comprehension

   leap_years = [year for year in range(1895, 1915) if year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)]
   print(leap_years)

..
  https://www.programiz.com/python-programming/list-comprehension
  https://www.py4u.net/discuss/191916
  https://en.wikipedia.org/wiki/Square_root_of_5

  https://www.mathsisfun.com/numbers/fibonacci-sequence.html