#!/usr/bin/env python3
# id: returns object identification

print("***********")
print("id checking")
print("***********")
x0 = 0                # an integer object is created
x1 = 1                # idem
print(id(x0), x0)
print(id(x1), x1, id(x1)-id(x0), "(difference in bits)\n")

print("*************")
print("type checking")
print("*************")
print("x0, type ::   ", x0, type(x0))
x0 = 'a'              # changing type from integer to string
print("x0, type ::   ", x0, type(x0))

print()   
print("****************")
print("strings as lists")
print("****************")
x0 = "I am a string"  # strings are ordered lists
x1 = " |  "  + x0[2] + x0[3]
print(x0, x1)

#!/usr/bin/env python3
from math import sqrt

print("Finding Triples  a^2 + b^2 == c^2") # ouput - not formatted
n = input("Maximum Number? ")              # input prompt
n = int(n)+1                               # casting to int
for a in range(1,n):                       # loop
  for b in range(a,n):
    ab_square = a**2 + b**2
    c = int(sqrt(ab_square))
    if (ab_square==c**2):                  # a^2 + b^2 == c^2
      print(f'{a:3d} {b:3d} | {c:3d}')     # formatted output

#!/usr/bin/env python3

text = "elements of string"
print()
print(text, "  |  ", text[9]+text[10])

print()
print("*********************")
print("iterating over values")
print("*********************")
ABC = ["A", "B", "C"]              # a list
print(ABC)
for strList in ABC:                # iterating over values
  print(strList + "_" + strList)

print()
print("**********************")
print("iterating over indices")
print("**********************")
for iList in range(n:=len(ABC)):   # walrus assignment (of n)
  ABC[iList] = 'new_' + ABC[iList]
print(ABC)
print("length of ABC : ", n)

print()
print("**********************************")
print("iterating over (index,value) pairs")
print("**********************************")
for index, value in enumerate(ABC):  
    print("(", index, "|", value, ")")

print()
print("*************************")
print("using list comprehensions")
print("*************************")
[print(strList) for strList in ABC]
print()

intList = [i for i in range(10)]
print(intList)

oddList = [value*value for value in intList if value%2==1]
print(oddList)

print()
print("********************")
print("tupeles come with ()")
print("********************")
# tuples are constant collections, viz unchangeable.
fruitTuple = ("apple", "banana", "cherry")
print(fruitTuple)

# would be an erorr
# fruitTuple[0] = "changing something constant"

#!/usr/bin/env python3

# second apple not stored (automatic duplicate elimination)
fruitSet = {"apple", "banana", "cherry", "apple"}

print("*********************************")
print("no ordering guranteed for sets {}")
print("*********************************")
print(fruitSet)
for fruit in fruitSet:
  if 'y' in fruit:
    fruit += " (which I like)"
  print(fruit)
print(fruitSet)

print()
print("**********************************")
print("dictionaries are associative lists")
print("**********************************")
anticCarDict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964,
  "colors": ["red", "white", "blue"]
               }
for key in anticCarDict:
  print(f'{key:7s} ::', anticCarDict[key])

#!/usr/bin/env python3

# [-1] : last entry
myList = [i for i in range(10,17)]
print(myList)
print(len(myList), " | ", myList[-1])

myList.append("not any more a list of interges")
print(myList)

myList.insert(1, "first")
print(myList)
print()

aList = [i for i in range(5)]
bList = [i for i in range(5,8)]
# myList = aList would make them the idential object
myList = aList.copy()            # copy entire list
print("aList  :: ", aList)
print("bList  :: ", bList)
print("myList :: ", myList)
print()

myList.extend(bList)             # extend list
print("aList  :: ", aList)
print("bList  :: ", bList)
print("myList :: ", myList)
myList.sort(reverse = True)      # sorting
print("myList :: ", myList)
print()

#!/usr/bin/env python3

# pass can be used also in for-loops
def nothingToDo():
  pass

# default argument, call by value
def flower(name='Iris'):
  print("my favorite flower is the ", name)
  name = "Orchid"

# list of arguments of arbitrary length
def allArgs(*args):
  for i in range(n:=len(args)):
    print(i, args[i])
  return n

# when using keys, the oder of calling does not matter
def keyFlowers(f3, f2, f1):
  print(f1, f2, f3)

print("*************")
print("call by value")
print("*************")
nothingToDo()
flower()
flower()
flower("Rose")

print()
myFlower = "Lily"
flower(myFlower)
print(myFlower)

print()
print("****************************")
print("arbirary number of arguments")
print("****************************")
print("argsLength: ", allArgs("Daffodil", "Dahlia", "Daisy"))

print()
print("*******************")
print("arguments with keys")
print("*******************")
# order does not matter with keys
keyFlowers(f2="Lavender", f1="Aster", f3="Poppy")

#!/usr/bin/env python3

import copy             # deep and schallow copy of objects

def myFunc(inList):
 inList.append(3)
 inList.extend([7,1])
 print("id/list in myFunc     :", id(inList), inList)
 inList.remove(7)
 print("id/list in myFunc     :", id(inList), inList)
 return

def newFunc(inList):
 inList.append(3)
 inList.extend([7,1])
 print("id/list in newFunc    :", id(inList), inList)
 inList = [3, 4, 6]                   # a new id is asigned
 print("id/list in newFunc    :", id(inList), inList)
 return

def valueFunc(inList):                # simulates call by value
 localList = copy.deepcopy(inList)    # deep == recursively
 localList.extend([77,11])
 print("id/list in valueFunc  :", id(localList), localList)
 return


print("******************************")
print("id not changed within function")
print("******************************")
myList = [1, 2]
print("id/list before calling:", id(myList), myList)
myFunc(myList)
print("id/list after calling :", id(myList), myList)

print("**************************")
print("id changed within function")
print("**************************")
myList = [1]                        # a new id is asigned
print("id/list before calling:", id(myList), myList)
newFunc(myList)
print("id/list after  calling:", id(myList), myList)

print("***********************")
print("simulated call by value")
print("***********************")
myList = [11]                        # a new id is asigned
print("id/list before calling:", id(myList), myList)
valueFunc(myList)
print("id/list after  calling:", id(myList), myList)

#!/usr/bin/env python3

# list argument with empty default
# the default is however updated at every call
def spammer(bag = []):
    bag.append("spam")
    return bag

# default is None, viz list does not exists
# None is an immutable object, the empty list [] not
def noProblem(bag = None):
    if bag is None:         # check if list exists
      bag = []
    bag.append("no spam")
    return bag

print("****************")
print("using \"bag = []\"")
print("****************")
print(spammer())
print(spammer())
print(spammer())
myBag = spammer()
myBag.clear()
print(myBag)
myBag = ["no"]
print(myBag)
spammer(myBag)
print(myBag)
spammer(myBag)
print(myBag)

print()
print("******************")
print("using \"bag = None\"")
print("******************")
print(noProblem())
print(noProblem())
print(noProblem())

#!/usr/bin/env python3

globalInt = 111

# the first string in a function body is the docstring
def hello():
    "function hello(): "    # the docstring
    globalInt = 22          # a local variable

    global helloInt         # becomes global
    helloInt = 33    
    return hello.__doc__

print()
print("*************")
print("scope testing")
print("*************")
a = 0
for i in range(4):
  b = i
  a += i
  print("   in loop: ", a, b)

print()
print("after loop: ", a, b)       
print()
print(" globalInt: ", globalInt )  

# helloInt only created if hello called at least once
# print("  helloInt: ",  helloInt )   

print()
print("*********")
print("docstring")
print("*********")
print(hello.__doc__ + "The docstring of the function hello ")
print(hello())

#!/usr/bin/env python3

def sum_recursion(n, k=0, result=0):
  "\sum_{k=0}^n k"
  if (k <= n):
    result = k + sum_recursion(n, k+1, result)
#   print(n, k, result)             # for testing
  return result

def fibonacci(n, k=1, kk=0):
  "sum of previous two numbers"
  print(n, k, kk)                   # for testing
  if (n > 0):
    n, k, kk = fibonacci(n-1, k+kk, k) 
  return n, k, kk                   # return 3 variables
   

print("*********")
print("recursion")
print("*********")
N = 4
print(f"evaluate \"\sum_{{k=0}}^{N:d} k\" via recursion:", sum_recursion(N))

print()
print("*******************")
print("compact asignements")
print("*******************")

_, resFib, _ = fibonacci(nFib:=8)      # with placehoders '_' (and Walrus)
print(f'\nthe {nFib:d}-the Fibonacci number is: ', resFib)