new_contents: # !/usr/bin/env python3
  # -*- coding utf-8 -*-
  # 1 and or not,与或非运算,bool值True,False
  # 2 // 地板除，整除,eg:
  >>> print(10 // 3)
  3
  # 3 ord(),chr()编码转换
  >>> ord('A')
  65
  >>> chr(66)
  'B'
  # 4 str.encode(type), str.decode('type')
  >>>'中文'.encode('utf-8')
  b'\xe4\xb8\xad\xe6\x96\x87'
  >>> b'\xe4\xb8\xad\xe6\x96\x87'.decode('utf-8')
  '中文'
  # 5 len(str)
  >>> len('hello')
  5
  >>> len('中文')
  2
  # 6 list，可增删改查 && tuple，readonly
  # list
  >>> fruit = ['apple', 'pear', 'banana']
  >>> fruit
  ['apple', 'pear', 'banana']
  # 查
  >>> fruit[-1]
  'banana'
  # 增
  >>> fruit.append('orange')
  >>> fruit
  ['apple', 'pear', 'banana', 'orange']
  >>> fruit.insert(2, 'grape')
  >>> fruit
  ['apple', 'grape', 'pear', 'banana', 'orange']
  # 删， 若无参数，则默认最后一个，有参数则删除指定位置
  >>> fruit.pop()
  'orange'
  >>> fruit
  ['apple', 'grape', 'pear', 'banana']
  # 改
  >>> fruit[2] = 'orange'
  >>> fruit
  ['apple', 'grape', 'orange', 'banana']
  # tuple 一旦初始化则不能改变，尽量使用tuple保证数据安全
  >>> t = (1, 23)
  >>> t
  (1, 23);
  # 若定义只有一个元素的tuple，应该用
  >>> t = (1,)
  >>> t
  (1,)
  # 因为数学公式中小括号的原因，若
  >>> t = (1)
  >>> t
  1
  # 7 条件判断if else; if elif else
  age = 18
  if age >= 18:
  	print('adult')
  elif age <= 6:
  	print('teenager')
  else:
  	print('nothing')
  # next start http://www.liaoxuefeng.com/wiki/0014316089557264a6b348958f449949df42a6d3a2e542c000/001431676242561226b32a9ec624505bb8f723d0027b3e7000
subject: add py note