#!/usr/bin/env python3

import os      # miscellaneous operating system interfaces

myText = "However fast you may be able to think,\nit is not fast enough."
f_out = open("output.txt", "w")       # output to file
f_out.write(myText)
f_out.close()                         # closing stream

os.system("cp output.txt input.txt")  # copy files

f_in = open("input.txt")              # reading is the default
print("# f_in :\n", f_in.read())      # file to string --> print
f_in.close()

print()
with open("input.txt", "r") as g_in:  # open with 'with'
  lineCount = 0
  for line in g_in:                   # reading line by line
    lineCount = lineCount + 1
    print(f'reading/printing line {lineCount:3d} ',line)

# cleaning up
if 1==2:
  os.remove("input.txt")
  os.remove("output.txt")

#!/usr/bin/env python3


# line continuations with ( ... )
myText = ( "However fast you may be able to think,\n"
         + "it is not fast enough.\n" 
         + "Don't worry, others have the same problem;)" )

# direct use of file streams
open("thinking.txt", "w").write(myText)
data = open("thinking.txt", "r").read()

# line continuations with  \
for token in data.replace('\n',' ').replace('.',' ').\
                  replace(', ',' ').replace('  ',' ').split(" "):
  print(token)

#!/usr/bin/env python3

def tokenizer(inString):
  sepChar = " "
  lastPos = 0
  inString = inString + sepChar     # seperation token
  for ii in range(len(inString)):
    if inString[ii] == sepChar:
      yield inString[lastPos:ii]
#      print(ii, inString, inString[lastPos:ii])
      lastPos = ii + 1

def fibonacci(maxN):
   x, y = 0, 1
   for _ in range(maxN):            # no variable needed
     x, y = y, x+y
     yield x


myText = "Warum bin ich hier?"
myList = [x for x in myText]
print("\nmyText\n",myText)
print("\nmyList\n",myList)
print()
myGenerator = tokenizer(myText)
print("type(myText)      : ", type(myText))
print("type(myList)      : ", type(myList))
print("type(myGenerator) : ", type(myGenerator))

print()
print("*** myList ***")
for cc in myList:
  print(cc, end='')                 # no endline
print()
print()

print("*** myGenerator ***")
for cc in myGenerator:
  print(cc, "",  end='')
print()

print("*********")
print("fibonacci")
print("*********")

[print(ff) for ff in fibonacci(5)]  # generator comprehension
print()
print(sum(fibonacci(5)))            # shortcut

#!/usr/bin/env python3
import math

def myLog(x):
  if not type(x) is float:
     raise TypeError("only myLog(x) if x is float")
  if x <= 0:
     raise Exception("only myLog(x) when x>0")
  return math.log(x)


print("************************")
print("basic exception handling")
print("************************")
try:
  print(x)
except NameError:
  print("undefined variable")
except:
  print("something went wrong")

print()
print("*******************************************")
print("catching user-defined exceptions / messages")
print("*******************************************")
try:
  myLog(0.0)
except TypeError as message:
  print("a type error occured: " + str(message))
except Exception as message:
  print("something went wrong: "   + str(message)) 
else:
  print("nothing went wrong")
finally:                                  # always executed
  print("'try except finally' finished")

print()
print("***********************")
print("input/output exceptions")
print("***********************")
fileName = "demo.txt"
try:
  f = open(fileName)                      # default, reading only
  try:
    f.write("Lorum Ipsum")
  except:
    print("failed to write to " + fileName)
  finally:
    f.close()
except:
  print("failed opening of " + fileName)

#!/usr/bin/env python3
import sys     # standard system modul
import os      # miscellaneous operating system interfaces

fN = 'counting.txt'

if not os.path.isfile(fN):            # 'is file'
  with open(fN, 'w') as f:            # short for try-catch block 
    f.write("1")

with open(fN, 'r+') as g:             # read and write
  if (var:=int(g.read())) >= 100000:  # exit when too large
    exit()
  print("content of ", fN, " : ", var)
  g.write("0")                        # appending, because did read first

print(sys.argv) 
os.system(sys.argv[0])                # running self

#!/usr/bin/env python3

import pickle

# any Python object:
# dictionary, list, ..
# instance of a class, tensor, ..
# lists of classes, tensors, ..
data = {'name': 'Alice', 'age': 30, 'city': 'New York'}

# binary serialization, dumping to file
with open('data.pkl', 'wb') as file:
    pickle.dump(data, file)

# deserialization, loading from file
with open('data.pkl', 'rb') as file:
    loaded_data = pickle.load(file)

print(loaded_data)