Python Day01


Chapter I

Introduction to Python

  1. Python 2: Source code is inconsistent and duplicated (updated and maintained until 2020)

    Python 3: Unified source code, no duplication

    Python 2: Python 2 print is not used, print “content”

    Python 3: Print in Python 3 must be enclosed in parentheses, print (“content”)

    Python 2: Input in digital Python 2 yields int

    Input in Python 3: Python 3 yields str

    Python is a dynamic interpretative strong type definition language

II. Variables

  1. Variable naming rules

    • It consists of numbers, letters and underscores.

    • You can’t start with numbers.

    • Be descriptive

    • Case-sensitive

    • Prohibit the use of Python keywords

    • Cannot use Chinese characters or Pinyin (low)

    • Recommended Writing of Variables

      • Hump body

      • Underline (Official Recommendation)

3. Constants

Variables are all named in capitals, which are constants.


  1. Single-Line Comments

    • It’s also called line commentary with #.

    • Comments for the current line

  2. multiline comment



    Three quotation marks, document annotations, and annotations describing the use of files or functions

V. Basic Data Types

  1. String str

    • “String asdasdasdada”

      • STR + str (string splicing)

      • STR * int (splicing strings multiple ints)

  2. Plastic (digital) int

    • Used for comparison and calculation

      Python 2: When dividing, it returns an integer (take the integer down)

      Python 3: The decimal (floating point) returned by Division

  3. Boolean bool

    • Used for judgment

      • True – True

      • False – False

VI. User Interaction

  1. Input — Input: Input in Python 3 gets strings

  2. Print — Output

    number = input("Please enter your content:")

7. Viewing Data Types

  1. type

    • View data types

      • Int (str) – Converting strings into integers

      • STR (int) – Converting integers to strings

    Type (object to be detected)

8. Process Control Statements

  1. Single if

    • If condition:

      Indentation result

      money = 10
      print("Starting from School")
      if money >= 10:
         print("Buy a fried chicken")
         print("Buy a beer")
      print("Walk, walk")
  2. Two choices, if else

    • If condition:

      Indentation result


      Indentation result y

      if 3>2:
         print("If this is done")
         print("This is otherwise implemented")
  3. Choose one more or no if elif elif elif

    • If condition:

      Indentation result

      Elif condition:

      Indentation result

      Elif condition:

      Indentation result

      if 1>2:
         print("This is A")
      elif 1>6:
         print("This is B")
      elif 1>5:
         print("This is C")
      elif 1>4:
         print("This is D")# No output without meeting the requirements
  4. Choose one more if elif elif else

    • If condition:

      Indentation result

      Elif condition:

      Indentation result

      Elif condition:

      Indentation result

      else :

      Indentation result

      if 1>2:
      elif 2>3:
      elif 5>6:
  5. If nesting

    • If condition:

      Indentation result

      If condition:

      Indentation result

    if score > 500:
       if score > 700 :
           print("Tsinghua University of Peking University")
           print("Find a university at will")
       print("Not enough points to go to college")

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