week1 notebook1

First acquaintance with Python 

1. Introduction to python 

- Interpreter: 
    cpython (default) 
    ipython(shell) 
    jpython(java) 
    ironpython 
    rubypython 

- encoding: 
    ascii: use one byte = 8 bits to identify everything that the computer can express 
    unicode: universal code , use 4 bytes = 32 bits for the corresponding relationship 
    utf-8: compress for the universal code, use at least 1 byte to represent 
    gbk: the corresponding relationship for the text of Asian countries 
        Chinese 2 bytes = 16 bits 
     Note : Chinese occupies 3 bytes in utf-8 encoding, and Chinese occupies 2 bytes in gbk 

- Version: 
    python2: interpreter default encoding: ascii 
            format: # -*- coding:utf-8 -*- 

    python3: interpreter Default encoding: utf-8 
            format: no need to configure encoding format 

- IDE: 
     - pycharm 
            - text size 
            - template 
     - vim 
     - notepad 

Second, module: 
    - time:
            The time module provides various time-related functions. 
            Time-related modules include: time, datetime, calendar 

    - getpass: 
            encrypted input password 

    - os: 
            contains common operating system functions 


3. Syntax: 

- Input, output: 
        print: 
            print(" You are crazy, he is stupid") 
        input: 
            # cipher text password 
            # import getpass 
            # user = input("enter a user,please") 
            # passwd = getpass.getpass("enter a num,please") 
            # print(user ,passwd) 

- variable: 
        Format: variable name = value 
        Specification: 
            a. Numbers, letters, underscores 
            b. Cannot start with numbers 
            c. Cannot use python keywords 
            Suggestion: Concise and understand; user_pwd = "xxx"
         Example:
                name = 'anthony' 
             user = 'anthony' 

- data type: 
        age = 18 # integer type 
        name = "anthony" # string type 
        list: 
         user_list = ["Lagerstroemia","Erkang","18","Mass" ,"Chicken"] 
         n3 = user_list[0] 
         n4 = user_list[1] # "Erkang" 

         user_list = ["Lagerstroemia","Erkang","18","Mass","Chicken"] 

         for xxx in user_list: 
            print(xxx) 
            if xxx == '18': 
               break 
      dictionary: 
         user_info = {"name":"Lagerstroemia","age":18} 


         n5 = user_info["name"]
         n6 = user_info["age"]

         user_info['count'] = 666
         # {"name":"紫薇","age":18,"count":666}

      Data type nesting: 

         n7 = ["alex","eric",[11,22,33]] 

         n7[1] 
         n7[2][1] 

         n8 = [ 
            "alex", 
            {'name':'day and day ','age':18}, 
            [11,22,33] 
         ] 
         n8[1]["age"] = 19 


- Conditional statement: 
    Format: 
        Format 1: 
         if Condition: 
            go here after success 

      Format 2: 
         if condition: 
            Go here after success 
         else: 
            go here after failure 

      Format 3: 
         if condition: 
            go here after success 
         elif condition: 
            go here after success 
         elif condition:
            After success go here 
         else:
            All of the above fail 
   Example: 

# while True: 
# # Define category 
# msg = ''' 
# Welcome to the big world 
# 1, Coke 
# 2, Sprite 
# 3, Lemon Tea 
# 4, Exit 
# ''' 
# # print Category 
# print(msg) 
# # Define options 
# choice = input("Please enter the category you choose:") 
# 
# # Judge the selected category 
# if choice == '1': 
# print("1, Vodka\n2, wine\n3, liquor 4, exit") 
# # Define wine category 
# search_type = input("Please enter your selected wine category:") 
# if search_type == '1': 
# print ("Vodka") 
# elif search_type == '2': 
# print("Wine")
#         elif search_type == '3':
# print("baijiu") 
# else: 
# print("input error") 
# break 
# elif choice == '2': 
# print("Sprite") 
# elif choice == '3': 
# print("lemon茶") 
# elif choice == '4': 
# break 
# else: 
# print("Input error") 

- Loop statement: 
    Format: 
        while Condition: The 
            condition is met and execute 

      while True: 
         print('Fishing is to fish for saury, and for saury Go to the island to fish') 

      while 1==1 and 2==2: 
         print('Fishing to catch saury, saury to fish on the island') 

      timer = 0 
      while timer < 3: 
         print('Fishing to catch saury, saury to go fishing on the island) 
         timer = timer + 1 

      print ('完成')

    Example: 
        # count = 1 
        # while count < 11: 
        # if count == 7: 
        # count +=1 
        # continue 
        # print(count) 
        # count +=1 

- Loop exit: 
    - break: 
            Definition: Forcibly terminate the current loop 
            Example: 
                Example 1: 
                        while True: 
                    print('fishing to catch saury, saury to fish on the island') 
                    break 
            Example 2: 
                    output 1 - 10 on the page 

                a. count = 1 
                    while count < 11: 
                       print(count) 
                       count = count + 1

                b. count = 1 
                    while True: 
                       print(count) 
                       count = count + 1 
                       if count == 11: 
                          break 

                c. count = 1 
                    while True: 
                       print(count) 
                       if count == 10: 
                          break 
                       count = count + 1 
   - continue : 
           Definition: Jump out of this cycle and continue to the next cycle. 
            Example: 
                Example 1: 
                    a. count = 1 
                    while count < 11: 
                       if count == 7:
                          count = count + 1 
                          continue 
                           print(count) 
                       count = count + 1 


                b. count = 1 
                    while count < 11: 
                       if count == 7: 
                          pass 
                       else: 
                          print(count) 
                       count = count + 1 

- looping exercise: 
    a. 1 Sum of all numbers of -100 
        # define base 
        sum = 0 
        count = 1 

        # loop start 
        while True: 
            if count == 100: 
                break 
            else:
                count += 1
                sum += count
        print(sum)

     b. 1-2+3-4+5 ... 99的所有数的和
        sum = 0
        for count in range(1,101):
            if count % 2 == 1:
                sum -= count
            elif count % 2 == 0:
                sum += count
        print(sum)