Python_0 basic learning_day02

Time:2019-9-7

Section II

One, while

While is also called infinite loop and dead cycle.

  1. While condition:

    Indentation circulator

    • Applications: Music playback: single track loop, list loop, random playback (also regular)

      Landing Interface:…

      Mathematical calculation: sum of 1-100, sum of 1-100 odd and/or even numbers…

    while True:
       print('-------------')
       print('Northwest Xuan Tian is a cloud,')
       print(The crow falls into the Phoenix flock.
       print('The table is full of heroes'.
       print('Who is the king and who is the minister? )

     

    • break– Must be recycled while

      braek– Terminates the current loop and the code below it does not execute.

      while True:
         print('-------------')
         print('Northwest Xuan Tian is a cloud,')
         print(The crow falls into the Phoenix flock.
         print('The table is full of heroes'.
         print('Who is the king and who is the minister? )
         break # After any conditions that can be placed under the circulating body
    • Changing the conditions of the circulating body— You can also terminate the cycle.

      f = True
      while f:
         print('-------------')
         print('Northwest Xuan Tian is a cloud,')
         print(The crow falls into the Phoenix flock.
         print('The table is full of heroes'.
         print('Who is the king and who is the minister? )
      f = False # After any conditions that can be placed under the circulating body

       

    • continue— Jump out of this loop and continue with the next one, and the code below will not execute.

      (The last line of code disguised as a loop)

      while True:
         print('-------------')
         print('Northwest Xuan Tian is a cloud,')
         print(The crow falls into the Phoenix flock.
         print('The table is full of heroes'.
         continue # Disguised as the last line of code, do not execute the following code, continue the wireless loop
         print('Who is the king and who is the minister? )
  1. Exercises

    1. # Use the while statement to write the guess size game: Set an ideal number such as: 66, let the user enter the number, if larger than 66, then show the guess result is larger; if smaller than 66, it shows the guess result is smaller; only equal to 66, show the guess result is correct, and then exit the loop.
      num = 66 # Setting variables for later maintenance
      while True: # Set an infinite loop
         s = int(input("Guess what integer the emperor is thinking of:")# User Interaction
         if s > num:
             print("Great results")
         elif s < num:
             print("The result is small")# If the input number does not satisfy the requirement, it will circulate indefinitely.
         else:   # satisfies s = 66
             print("The results are correct")
             break  # Termination
    1. # Upgrade on the basis of Question 1: Give users three guesses. If they guess correctly within three times, they will show that they guessed correctly. If they don't guess correctly within three times, they will automatically exit the circle and show that'You are too stupid'.
      count = 0
      num = 66
      while count < 3: # Set limits on variables
         s = int(input("Guess what number the emperor is thinking of:")
         if s > num:
             print("Great results")
         elif s < num:
             print("The result is small")
         else:
             print("The results are correct")
             break
         count = count + 1  # Change the variable, change the condition to False, and terminate the loop
      else:
         print("It's silly of you!"
    1. # Output 12 3 4 5 6 8 9 10 using while loop
      # Pay attention to reading, No 7
      # Method 1
      num = 0
      while num < 10:
         num += 1
         if num == 7:
             continue  # When num is 7, end this cycle and continue next time
         print(num)
      # Method 2
      num = 0
      while num < 10:
         num += 1
         if num == 7:
             num += 1 # When num is 7, 7 + 1
         print(num)  
    1. # Output all odd numbers in 1-100
      # Method 1
      num = 1
      while num < 100:
         print(num)
         num += 2   # The variable is 1, plus two each time, and the output is odd.
      # Method 2
      num0 = 1
      while num0 < 101:
         if num0 % 2 == 1: # Divide variables by 2 and then output
             print(num0)
         num0 += 1
    1. # All Even Numbers in Output 1-100
      # Method 1
      num1 = 0
      while num1 < 100:
         num1 += 2 # Every time you add two, the variable is zero, the output is even.
         print(num1)
      # Method 2
      num2 = 1
      while num2 < 101:
         if num2 % 2 == 0: # Variable 2, remainder 0, is even
             print(num2)
         num2 += 1
    1. # Find the sum of all numbers of 1-2+3-4+5... 99
      num4 = 0
      ss = 0
      while num4 < 99:
         num4 += 1
         if num4 % 2:  # Find the odd number and add it up.
             ss += num4
         else:         # Find the even number, then the odd number minus the even number.
             ss -= num4
      print(ss)

Formatting

The positions occupied must be filled one by one, and filled in order, from left to right.

applicationFor example, make a business card, register an account…

  1. %s—— String type

  2. %d%i—— Number type

    name = input("name:")
    age = input("age:")
    addr = input("addr:")
    phone = input("phone:")
    info = """
    -----------info----------
    Name:%s
    Age:%s
    Company:%s
    Telephone:%s
    ------------end-----------
    """%(name,age,addr,phone)
    print(info)

     

  3. %%—— Transliteration

    msg = "% s is 2%"%(python)
    print(msg)#%% Transliteration is two percent

     

  4. F “{Format}”—— The Best Filling

    # An Application of f"{}"
    msg = f"""-----------info----------
    Name: {input ('name:')}
    Age: {input ('age:')}
    Company: {input ('addr:')}
    Telephone: {input ('phone:')}
    ------------end-----------"""
    print(msg)
  1. Exercises

# User login (three error opportunities) prompts for the number of input errors, the number of remaining inputs (combination of while and formatted output)
count = 4
s1 = 0
while count > 1:
   count -= 1
   id = input("Please enter your account:")
   psd = input("Please enter your password:")
   if id == "username" and psd == "password":
       print("Landing Success")
       break
   else:
       s1 += 1
       print(F "Input error {s1} times and {count - 1} times again")

 

Operators

  1. Arithmetic operator

    operator describe Example
    + Add, add two objects together a+b=30
    Subtraction, subtraction of two objects, may result in negative numbers a-b=-10
    * Multiply, match two numbers, or return a string that has been repeated several times a*b=200
    / Except, two objects divide b/a=2
    % Take the membrane and return the remainder of the Division b%a=0
    ** Power, returning the Y power of X a**b=100000000000000000000L
    // The integer part of a quotient. a//b=0
  2. Comparison operator

    operator describe Example
    == Comparing two objects is equal. A==b returns False
    != Not equal. Compare two objects to see if they are not equal. A!= B Returns True
    <> Not equal. Compare two objects to see if they are not equal. A<>b Returns True
    > Comparing whether x is greater than y, A > B returns to False
    < Comparing whether x is less than y A < B returns to True
    >= If x is greater than or equal to y, compare whether x is greater than or equal to y. A >= B returns False
    <= If x is less than or equal to y, compare whether x is less than or equal to y. A<= B returns True
  3. Assignment Operators

    operator describe Example
    = Assignment Operators C = a + b, assign the result of a + B to C
    += Additive assignment operator C += A is equivalent to C = C + A
    -= Subtraction assignment operator C – = a is equivalent to C = C – A
    *= Multiplication assignment operator C *= A is equivalent to C = C * a
    /= Division assignment operator C/= A is equivalent to C = C / A
    %= Modular assignment operator C% = a is equivalent to C = c% = a
    **= Power assignment operator c = A is equivalent to C = C a
    //= Dividing assignment operator C /= A is equivalent to C = C // a
  4. Logical Operator

    operator describe Example
    and “And” A and B return true
    or “Or” A or B returns true
    not “No” No (a and b) returns false

    andAll are true, that is true: choose the content after and

    One is false, the other is false: when both are false, choose the content before and

    or As long as there is one truth, it is true.

    Both are true. Choose or

    Both are false: the one behind or

    notNo, No.

    • Priority: () > not > and > or

     

    9 or 8 and 4 and not 4 < 5 or 8
    9 or 8 and 4 and False or 8
    9 or 4 and False or 8
    9 or False or 8
    9 or 8
    9

    not 3<5 and 6>3 or 6 and not True or False and 8 or 90
    False and 6>3 or 6 and not True or False and 8 or 90
    False and 6>3 or 6 and False or False and 8 or 90
    False or 6 and False or False and 8 or 90
    False or  False or False and 8 or 90
    False or False or False or 90
    90
  5. member operator

    operator describe
    in If a value is found in the specified sequence, it returns True, otherwise it returns False.
    not in Returns True if no value is found in the specified sequence, otherwise false
    a = "alex"
    if "b" not in a:
       print("No")
    else:
       print("In"
       
    a = "alex"
    if "b" in a:
       print("In"
    else:
       print("No")
  1. Operator exercises

# I deduce it first, then print it.
Judge True of the following logical statements,False.
1 > 1 or 3 < 4 or 4 > 5 and 2 > 1 and 9 > 8 or 7 < 6
# True
not 2 > 1 and 3 < 4 or 4 > 5 and 2 > 1 and 9 > 8 or 7 < 6
# False
Find the values of the following logical statements.
8 or 3 and 4 or 2 and 0 or 9 and 7
# 8
0 or 2 and 3 and 4 or 6 and 0 or 3
# 4

Preliminary knowledge of coding

  1. ASCII code—— American self-made, the earliest 256

    English 1 byte

    Chinese is not supported

  2. Gbk—— Made in China includes ASCII

    Chinese Standard Language-National Standard

    English 8 bits 1 byte, Chinese 16 bits 2 bytes

  3. unicode—— Universal Code

    English 32-bit 4 bytes

    Chinese 32-bit 4 bytes

  4. utf-8—— Upgraded version of Universal CodeThe Most Popular Codebook

    English 1 byte 8 bits

    Europe 2 bytes 16 bits

    Asia 3 bytes 24 bits

V. Unit Conversion

  • 1Bytes = 8bit 1 byte = 8 bits

  • 1KB = 1024B

  • 1MB = 1024KB

  • 1GB = 1024MB

  • 1TB = 1024GB

  • 1PB = 1024TB

  • 1EB = 1024PB

 

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