* 2020-06-17
** note
  - ex44.py
    - none
* 2020-06-15
** note
  - ex43.py
    - none
* 2020-06-12
** note
  - ex42.py
    - MRO(method resolution order)
* 2020-06-10
** note
  - ex40.py
    - none
  - ex41.py
    - none
* 2020-06-08
** note
  - ex37.py
    - none
  - ex38.py
    - ten_things.split(' ') == split(ten_things, ' ')
    - more_stuff.pop() == pop(more_stuff)
    - stuff.append(next_one) == append(stuff, next_one)
  - ex39.py
    - dictionaries do not use index number to search a key or a value.
* 2020-05-29
** note
  - ex32.py
    - remove, insert, index, append, '+' and del
  - ex33.py
    - none
  - ex34.py
    - none
  - ex35.py
    - none
  - ex36.py
    - none
* 2020-05-27
** note
   - ex27.py
     - none
   - ex28.py
     - <= (greater than or equal to), =< (less than or equal t0)
   - ex29.py
     - The 'if' means to test criteria.
     - The 'if' processes the script is intended.
     - If the script is not indented, an error should be occured.
   - ex30.py
     - none
   - ex31.py
     - none
* 2020-05-25
** note
   - ex23.py
     - none
   - ex24.py
     - none
   - ex25.py
     - none
   - ex26.py
     - none
* 2020-05-22
** note
   - ex15.py
     - The argument method is better than using stdin. becouse bash-completion could be used.
     - python3.8 shell
       - >>> filename=input()
       - ex15_sample.txt
       - >>> txt = open(filename)
       - >>> txt_script = txt.read()
       - >>> print(txt_script)
       - This is stuff I typed into a file.
       - It is really cool stuff.
       - Lots and lots of fun to have in here
   - ex16.py
     - 'w' is to open a file on write mode.
     - If a file is openned with 'w', target.truncate() should not be need. the 'w' mode always overwrite a file.
   - ex17.py
     - cat is concatenate files to stdout
     - If file.close() is not called, the file which is openned by python chould not be modified on orther programs.
   - ex18.py
     - none
   - ex19.py
     - none
   - ex20.py
     - file.seek is to move to new file posotion
   - ex21.py
     - none
   - ex22.py
     - none
* 2020-05-20
** note
   - ex8.py
     - none
   - ex9.py
     - none
   - ex10.py
     - none
   - ex11.py
     - none
   - ex12.py
     - pydoc input
       - describe input on python. It looks like man commnad on linux shell.
   - ex13.py
     - none
   - ex14.py
     - none
* 2020-05-18
** note
   - ex1.py
     - # is commnet.
   - ex2.py
     - I do't find mistakes.
   - ex3.py
     - none
   - ex4.py
     - car_pool_capacity is not defined.
   - ex5.py
     - none
   - ex6.py
     - + is to add two string array.
   - ex7.py
     - none
