2019.07.17 study notes (program loop control)

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

III., And combinations conditional

1. Analyzing conditions

Operators	Mathematics Symbol	description
<	<	Less than
<=	≤	Less than or equal
>=	≥	greater or equal to
>	>	more than the
==	=	equal
!=	≠	not equal to

2. The combination of conditions

Operators, and use	description
x and y	Two logic conditions are x and y and
x or y	Or two logical conditions of x and y
not x	X is the logical NOT condition

3. Analyzing conditions and combinations

• guess = eval(input())
  if guess > 99 or guess < 99:
      print("猜错了")
  else:
      print("猜对了")

IV. Exception Handling

1. The basic exception handling using

• try:
  <语句块1>
  except:
  <语句块2>
  
  try:
      num = eval(input("请输入一个整数: "))
      print(num**2)
  except:
      print("输入不是整数")

• # 示例
  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

2. The use of high-level exception handling

• finally4 corresponding to a certain block of statements executed
• else3 corresponds to a block of statements executed when an abnormality occurs

try:
    <语句块1> 
except:
    <语句块2> 
else:
    <语句块3> 
finally:
    <语句块4>

V. loop 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')

4.break和continue

• and end the current break out of the entire cycle, the statement after the execution cycle
• break out of only the innermost loop current
• When the end of the cycle continue, continue to perform the subsequent cycles
• break and continue can be used with the for and while loops
• When the cycle is not exit the break statement, the else statement block

The string traversal

• s is a string, each character string traversed, generation cycle

  for c  in  s: 
      <语句块>

6. The list loop through

• ls is a list, each element traversing, generation cycle

  for item  in  ls:
      <语句块>

Six .random module

1.random generate random numbers

random library using the Python standard library of random numbers

• Pseudorandom number: using (pseudo) random sequence of Mersenne Twister generated element
• random serves mainly for generating a random number

• Use random library:import random

• 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. The basic function of the random number

function	description
seed(a=None)	Initialized with the given random number seed, the default is the current system time
random()	Generating a random decimal between [0.0, 1.0)

function	description
Randine (a, b)	Generating an integer between [a, b]
randrange (m, n [k])	Generating a [m, n) in between steps k is a random integer
getrandbits (k)	getrandbits (k)
uniform(a, b)	Generating a random decimal between [a, b]
choice(seq)	Select a random element from a sequence seq
shuffle(seq)	Seq sequence elements in a random arrangement, the sequence returns to disrupt

import random

random.seed(10)  # 产生种子10对应的序列
random.random()

3.time () custom function

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

Computing VII. 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)

operation:

1. 使用while循环输出1 2 3 4 5 6     8 9 10
2. 求1-100的所有数的和
3. 输出 1-100 内的所有奇数
4. 输出 1-100 内的所有偶数
5. 求1-2+3-4+5 ... 99的所有数的和
6. 用户登陆（三次机会重试）
7：猜年龄游戏
要求：
    允许用户最多尝试3次，3次都没猜对的话，就直接退出，如果猜对了，打印恭喜信息并退出
    
8：猜年龄游戏升级版(选做) 
要求：
    允许用户最多尝试3次
    每尝试3次后，如果还没猜对，就问用户是否还想继续玩，如果回答Y或y, 就继续让其猜3次，以此往复，如果回答N或n，就退出程序
    如何猜对了，就直接退出 
    
    
9.for循环打印99乘法表

10.for循环打印金字塔:如下
    *
   ***
  *****
 *******
*********

1.使用while循环输出1 2 3 4 5 6     8 9 10
count = 0
while count < 10:
if count == 6:
    count += 1
    continue
count += 1
print(count,end=' ')

2.求1-100的所有数的和
sum=0
count=0
while count<100:
    count +=1
    sum+=count
print(sum)

3.输出 1-100 内的所有奇数
count=1
while count<100:
    if count % 2==1:
     print(count,end=' ')
    count+=1
    
    
4.输出 1-100 内的所有偶数 
count=1
while count<=100:
    if count % 2==0:
     print(count,end=' ')
    count+=1
    
5.求1-2+3-4+5 ... 99的所有数的和
sum=0
for i in range(1,100):
    if i%2==0:
        sum -=i
    else:
        sum+=i
print(sum)


6.用户登陆（三次机会重试）
id='1608210104'
pw='123456'
for i in range(3):
    id1 = input('Please your enter id：')
    pw1 = input('Please your enter password（您只有三次机会）：')
    if id1==id and pw1==pw:
        print('you enter is True（你已登录成功）')
    else:
        print('you enter is False')
print('三次机会已用完')


7.猜年龄游戏
age='18'
for i in range(3):
    age1 = input('Please your enter age：')
    if age1==age:
        print("your answer is very True")
        break
    else:
      continue

8.猜年龄游戏升级版(选做)
要求允许用户最多尝试3次# 每尝试3次后，如果还没猜对，就问用户是否还想继续玩，如果回答Y或y, 就继续让其猜3次，以此往复，如果回答N或n，就退出程序# 如何猜对了，就直接退出
i=0
age=18
while i!=3 :
    age = input("Please your enter age：")
    if age== 18:
        print("your answer is True")
        break
    i += 1  # 计数器就加1

    if i == 3:  # 次数
        ret = input("是否还想玩（Y/N）：")
        if ret == "Y" or ret =="y":

9.for循环打印99乘法表
for i in range(1,10):
    for j in range(1,i+1):
        print(f'{i}*{j}={i*j}',end='  ')
    print()
    
10.for循环打印金字塔:如下
for i in range(1,6):
        print(f"{'*'*(i+i-1): ^9}")