2019.07.16 study notes (python program volume control structures)

A. Review Review (basic data types)

1. Digital Type

(1) integer

• x = int(10)
  pow(x, 10)

(2) Float

• y = float(10)  # 10.0
  print(round(0.1 + 0.2, 1) == 0.3)

2. Operator

• +-*/ // % **

3. String

• name = str(10)  # '10'
  name = 'nick'
  name = "nick"
  name = "nick's"# 双引号可以包裹单引号
  name = """
  nick's 
  name 
  is "nick"
  """  # 三双引号里的字符串可以换行

4. The built-in method

• name.split()  # 指定字符串分割
  name.startswith('n')#从头开始匹配 
  name.endswith('k')# 从尾开始匹配
  print(name.center(50, '*')) # 从中间开始补充字符*，总长度50

The escape character

• s = "nick's name is \"nick\""
  s = '\t' # 缩进
  print(s)
  s = '\n' # 换行
  print(s)
  s = r'\t\n' # \r原位打印，和end=''成对使用
  print(s)
  
  for i in range(5):
      print('1',end=',')

Two control structure of a program

1. The branched structure

• Single branch

• Usually for determining if the scene / selection

• 90 points or more outstanding

  score=95
  if score>90:
      print('优秀')

• Dual Branch

• if ....else

• More than 90 points outstanding, 90 points or less good

  score=95
  if score>90:
    print('优秀')
  else：
    peint('良好')

• A triplet of expressions

   score=75
      print('优秀')if score>90 else print('良好')# 单分支没有，多分支也没有
      #结果一 条件 结果二

• Multi-Branch

• Elif Elif .... if .... else ......

• 90 more than excellent, 90-70 good, about 70 fail

  score=95
  if score>90:
    print('优秀')
  elif score>70:
    peint('良好')
  else:
      peint('及格')

• if......if......if......if

  score=95
  if score>90:
    print('优秀')
  if score>70 and score<90:
    peint('良好')
  if score<60:
      peint('及格')

2. Logical Operators

• > >= < <= == !=

• and 两者都必须成立

• or 其中一个成立即可

• not 非

3. Exception Handling

• try:
      y = int(input('数字：'))  # 10
      y += 10 # y = y + 10
  except Exception as e:
      print(f'error: \033[1;35m {e} \033[0m!')
  finally:  # 无论报不报错，都会执行finally下面的代码
      print(1)
  
  Exception# 异常处理的时候，只要写这个就可以了
  raise  # 自定义报错
  assert 断言()
  assert 1==2

III. Cyclic structure of the program

1.for circulation

• for i in range(1,10,2): 
       print(i)# [1,3,5,7,9],输出的就是1-10之间的奇数
  for i in 'nick':
      print(i)# n,i,c,k每个字符换行输出

2.while cycle

• continue和break的区别
  # continue不执行下面代码,继续运行循环
  count = 0
  while count < 100: # 49
      if count == 49:
          count += 1
          continue  # 不执行下面代码,继续运行循环
      count += 1 # 50   跳过不打印
      print(count) # 50
  
  # break终止循环  结束本次的while循环
  count = 0
  while count < 100: # 49
  
      if count == 49:
          count += 1
          break  # 终止循环    结束本次的while循环
      count += 1 # 50
      print(count) # 50

3.while.....else

• count = 0
  while count < 100: # 49
      if count == 49:
          count += 1
          break # 终止循环
      count += 1 # 50n
      print(count) # 50
  else:  #正常跳出循环的时候会执行,异常中断不执行
      print('打我')

Four .random module

1.random generate random numbers

• import random
  random.seed(10) # 种子 # 如果不自定义种子,则种子按照当前的时间来
  print(random.random())# 取0和1之间的小数
  print(random.choice([1,1,2,3,4]))

2.time () custom function

• # 自己造的一个随机数
  import time
  time=time.time()
  print(str(time).split('.')[-1][-1])

Calculation V. pi

• # Π
   pi = 0
   k = 0
   while True:
   pi +=  (1/(16**k))* \
             (4/(8*k+1) - 2/(8*k+4) - 1/(8*k+5) - 1/(8*k+6))# 数学求Π的公式
    print(pi)
    k += 1
  
  
  # 蒙特卡洛方法求Π
  import random
  
  count = 0
  for i in range(100000):
      x, y = random.random(), random.random()
      dist = pow(x ** 2 + y ** 2, 0.5)
      if dist < 1:
          count += 1
  print(count / 100000 * 4)