python初学-基本语法语句汇总

傷城~ 2022-09-11 05:11 193阅读 0赞

#参考:笨办法学法学Python3（（Learn Python3 The Hard Way 中文版）中文版
    print("This will run.")#使用单引号也可以print('This will run.')
    # A comment,Anything after the # is ignored by python.
    # print("This won't run.")
    print(3 + 2 < 5 - 7)   #直接进行计算,然后输出的是 False
    print("Is it greater or equal?", 5 >= -2) #输出Is it greater or equal? True
    cars = 100
    print("There are", cars, "cars available.") #There are 100 cars available.
    #4.0 是一个浮点数,会自动进行浮点计算.
    #用单引号或双引号把一段文本引起来，就是在创建一个字符串.比较短的字符串应该用单引号.
    #把你需要的变量放在 {} 里面就可以把变量当作字符嵌入在字符串中。你必须要在字符串前面加上字母 f （代表 format），比如 f"Hello, {somevar}" 。双引号前面的 f 是为了告诉 python3： “这个字符串需
    #要被格式化，把这些变量放在那儿。”
    my_name = 'Zed A. Shaw'  #这样也行: my_name ="Zed A. Shaw"
    my_age = 35 
    my_height = 74 
    my_weight = 180 
    print(f"{my_name} have {my_age}, {my_height}, and {my_weight}.")#Zed A. Shaw have 35, 74, and 180.
    #何我如何给浮点数四舍五入取整数？浮点数四舍五入取整数？你可以用 round() 函数，比如：round(1.7333),结果为2 。
    #######################################################ex6.py
    types_of_people = 10
    x = f"There are {types_of_people} types of people."
    
    binary = "binary"
    do_not = "don't"
    y = f"Those who know {binary} and those who {do_not}."
    
    print(x)
    print(y)
    
    print(f"I said: {x}")
    print(f"I also said: '{y}'")
    
    hilarious = False
    joke_evaluation = "Isn't that joke so funny?! {}"
    
    print(joke_evaluation.format(hilarious))#str.format()语法使用使用花括号 {} 来包围待替换的字符串。在花括号 {} 中可以使用位置索引或关键字索引来按顺序或匹配关键字依次替换。
    print("Its fleece was white as {}.".format('snow'))
    w = "This is the left side of..."
    e = "a string with a right side."
    
    print(w + e)#使用 + 来连接字符串
    ##############################################输出
    '''
    $ python ex6.py
    There are 10 types of people.
    Those who know binary and those who don't.
    I said: There are 10 types of people.
    I also said: 'Those who know binary and those who don't.'
    Isn't that joke so funny?! False
    Its fleece was white as snow.
    This is the left side of...a string with a right side.
    '''
    ##########################################################
    print("." * 10) # 输出10个点 ..........
    print('Cheese')#print默认分行输出
    print('Burger')
    '''
    #输出
    Cheese
    Burger
    '''
    print('Cheese', end=' ')#end=指定分隔符
    print('Burger')
    '''
    #输出
    Cheese Burger
    '''
    
    print('Cheese', end='_')
    print('Burger')
    '''
    #输出
    Cheese_Burger
    '''
    #############################练习.format()语法使用
    formatter = "{}_{} {} {}"
    
    print(formatter.format(1, 2, 3, 4))
    print(formatter.format("one", "two", "three", "four"))
    print(formatter.format(True, False, False, True))
    print(formatter.format(formatter, formatter, formatter, formatter))
    print(formatter.format(
    "Try your",
    "Own text here",
     "Maybe a poem",
     "Or a song about fear"
     ))
    
    '''
    输出:
    1_2 3 4
    one_two three four
    True_False False True
    {}_{} {} {}_{}_{} {} {} {}_{} {} {} {}_{} {} {}
    Try your_Own text here Maybe a poem Or a song about fear
    '''
    ##############################
    days = "Mon Tue"
    #字符串前面加 \n 另起一行输出也可以 months = "\nJan\nFeb\n"
    months = "Jan\nFeb\n"
    
    print("Here are the days: ", days)
    print("Here are the months: ", months)
    #打印输出一段,在三个双引号之间加了空格会报错,你必须这样输入 """ ，而不能这样输入" " " ，也就是说中间不能加空格。
    print("""
     There's something going on here.
     With the three double-quotes.
     """)
    '''
    输出:
    Here are the days:  Mon Tue
    Here are the months:  Jan
    Feb
    
    
     There's something going on here.
     With the three double-quotes.
    '''
    ################学习“转义字符”（escape scequence）
    '''
    要在一个用双引号引起来的字符串中再加一对双引号，就像这样："I "understand" joe." ，
    python 就会懵掉，因为它会认为understand 后面的双引号就代表这个字符串已经结束了。所以你需要用一种方式告诉 python 字符串里面的双引号并不是一个真正的双引号。解决方法就是转义.
    第二种方法是用三个双引号，即 """ ，这样就能像字符串一样 赋值，而且你可以多输入几行，
    最后再以 """ 结尾即可。当然用三个单引号也可以''',最后再以 ''' 结尾即可.
    '''
    tabby_cat = "\tI'm tabbed in."
    persian_cat = "I'm split\non a line."
    backslash_cat = "I'm \\ a \\ cat."
    
    fat_cat = """
    I'll do a "list":
    \t* Cat 'food'
    \t* Fishies
    \t* Catnip\n\t* Grass
     """
    
    print(tabby_cat)
    print(persian_cat)
    print(backslash_cat)
    print(fat_cat)
    '''
    输出:
            I'm tabbed in.
    I'm split
    on a line.
    I'm \ a \ cat.
    
    I'll do a "list":
            * Cat 'food'
            * Fishies
            * Catnip
            * Grass
    '''
    ##########################################
    x = int(input())
    x = input()
    y = input("Name?")
    ###########################文件读取,可以使用pydoc open获取open函数的帮助
    from sys import argv # sys 是一个包（package），这个语句是说从那个sys包里获取 argv 功能（feature）
    
    script, user_name, filename = argv
    prompt = '> '
    
    print(f"Hi {user_name}, I'm the {script} script.")
    print(f"Do you like me {user_name}?")
    likes = input(prompt)
    
    print(f"""
    Alright, so you said {likes} about liking me.
    """)
    
    txt = open(filename)
    print(f"Here's your file {filename}:")
    print(txt.read())#执行不带参数的 read 命令！
    
    print("Type the filename again:")
    file_again = input("> ")
    txt_again = open(file_again)
    print(txt_again.read())
    '''
    PS F:\test\lpthw> python ex1.py lei txt_file.txt
    输出:
    Hi lei, I'm the ex1.py script.
    Do you like me lei?
    > YES
    
    Alright, so you said YES about liking me.
    
    Here's your file txt_file.txt:
    This file's content is:
        A,B,C
        file_end!
    Type the filename again:
    > txt_file.txt
    This file's content is:
        A,B,C
        file_end!
    '''
    ####################################文件操作
    
    from sys import argv
    from os.path import exists
    
    script, from_file, to_file = argv
    
    print(f"We're going to erase {from_file}.")
    print("If you don't want that, hit CTRL-C (^C).")
    print("If you do want that, hit RETURN.")
    input("Show your opinion >")
    '''
    we could do these two on one line, how?
    indata = open(from_file).read() ，这意味着你不需要在之后再输入 in_file.close() ，因为
    你已经到了脚本的最后。一旦那一行运行过之后，它就已经被 Python 关掉了。
    '''
    in_file = open(from_file, 'r+')#带一个 + ，可以让文件同时支持读和写
    indata = in_file.read()#执行完read语句后,文件指针指到末尾
    
    print(indata)
    print("Truncating the file. Goodbye!")
    in_file.seek(0)#需要先将文件指针指到起始位置才能truncate(删除文件内容)
    in_file.truncate()
    print("if no output means that truncate succeeded:",in_file.read())
    print("Now I'm going to ask you to input two lines.")
    line1 = input("line 1: ")
    line2 = input("line 2: ")
    
    print("I'm going to write these to the file.")
    in_file.write(line1)
    in_file.write("\n")
    in_file.write(line2)
    in_file.seek(0)#需要先将文件指针指到起始位置才能再read
    print(in_file.read())
    
    print(f"Copying from {from_file} to {to_file}")
    print(f"The input file is {len(indata)} bytes long")
    print(f"Does the output file exist? {exists(to_file)}")
    print("Ready, hit RETURN to continue, CTRL-C to abort.")
    input()
    
    in_file.seek(0)#需要先将文件指针指到起始位置才能再read
    indata = in_file.read()
    out_file = open(to_file, 'w+')
    out_file.write(indata)
    
    print("Alright, all done.")
    out_file.seek(0)#需要先将文件指针指到起始位置才能再read
    print(out_file.read())
    out_file.close()
    in_file.close()
    
    '''
    输出:
    PS F:\test\lpthw> python ex1.py txt_file.txt test.txt
    We're going to erase txt_file.txt.
    If you don't want that, hit CTRL-C (^C).
    If you do want that, hit RETURN.
    Show your opinion >
    This file's content is:
        A,B,C
        file_end!
    Truncating the file. Goodbye!
    if no output means that truncate succeeded
    Now I'm going to ask you to input two lines.
    line 1: file now begin:
    line 2: file is end!
    I'm going to write these to the file.
    file now begin:
    file is end!
    Copying from txt_file.txt to test.txt
    The input file is 47 bytes long
    Does the output file exist? True
    Ready, hit RETURN to continue, CTRL-C to abort.
    
    Alright, all done.
    file now begin:
    file is end!
    
    '''

#################函数定义方式###########################
    # this one is like your scripts with argv
    #第一种, *args未明确需要多少函数参数,一般不用
    def print_two(*args):
        arg1, arg2 = args
        print(f"arg1: {arg1}, arg2: {arg2}")
    
    #第二种,这是最常用的, that *args is actually pointless, we can just do this
    def print_two_again(arg1, arg2):  #以 : 结束这一行，另起一行开始缩进
        print(f"arg1: {arg1}, arg2: {arg2}") #缩进四个空格的所有行都是关于 print_two 这个函数名的函数体,缩进必须正好是4个空格,不多不少。
    
    #第三种 this just takes one argument
    def print_one(arg1):
        print(f"arg1: {arg1}")
    
    #第四种, this one takes no arguments
    def print_none():
        print("I got nothin'.")
    
    
    print_two("Zed","Shaw")
    print_two_again("Zed","Shaw")
    print_one("First!")
    print_none()
    '''
    输出
    arg1: Zed, arg2: Shaw
    arg1: Zed, arg2: Shaw
    arg1: First!
    I got nothin'.
    '''
    #####################给函数赋值的几种不同的方式
    def cheese_and_crackers(cheese_count, boxes_of_crackers):
        print(f"You have {cheese_count} cheeses!")
        print(f"You have {boxes_of_crackers} boxes of crackers!"
    
    
    print("We can just give the function numbers directly:")
    cheese_and_crackers(20, 30)#调用自定义函数
    
    
    print("OR, we can use variables from our script:")
    amount_of_cheese = 10
    amount_of_crackers = 50
    cheese_and_crackers(amount_of_cheese, amount_of_crackers)
    
    print("We can even do math inside too:")
    cheese_and_crackers(10 + 20, 5 + 6)
    
    print("And we can combine the two, variables and math:")
    cheese_and_crackers(amount_of_cheese + 100, amount_of_crackers + 1000)
    ##############函数和文件操作
    from sys import argv
    script, input_file = argv
    
    def print_all(f):
        print(f.read())
    
    def rewind(f):
        f.seek(0)
    
    def print_a_line(line_count, f):
        print(line_count, f.readline())
    
    
    current_file = open(input_file)
    
    print_all(current_file)
    rewind(current_file)
    
    print("Let's print three lines:")
    
    current_line = 1
    
    current_line += 1
    print_a_line(current_line, current_file)
    '''
    $ python ex20.py test.txt
    First let's print the whole file:
    This is line 1
    This is line 2
    This is line 3
    Now let's rewind, kind of like a tape.
    Let's print three lines:
    1        This is line 1
    2        This is line 2
    3        This is line 3
    '''
    #############################函数的返回值return
    def add(a, b):
        print(f"ADDING {a} + {b}")
        return a + b
    
    def subtract(a, b):
        print(f"SUBTRACTING {a} - {b}")
        return a - b
    
    def multiply(a, b):
        print(f"MULTIPLYING {a} * {b}")
        return a * b
    
    def divide(a, b):
        print(f"DIVIDING {a} / {b}")
        return a / b
    
    
    print("Let's do some math with just functions!")
    
    # A puzzle for the extra credit, type it in anyway.
    print("Here is a puzzle.")
    
    what = add(10, subtract(20, multiply(30, divide(40, 2))))
    
    print("That becomes: ", what,"\nCan you do it by hand?")
    '''
    Let's do some math with just functions!
    Here is a puzzle.
    DIVIDING 40 / 2
    MULTIPLYING 30 * 20.0
    SUBTRACTING 20 - 600.0
    ADDING 10 + -580.0
    That becomes:  -570.0
    Can you do it by hand?
    '''
    #######################################函数返回多值
    def secret_formula(started):
        jelly_beans = started * 500
        jars = jelly_beans / 1000
        crates = jars / 100
        return jelly_beans, jars, crates
    
    
    start_point = 10000
    beans, jars, crates = secret_formula(start_point)
    print("With a starting point of: {}".format(start_point))
    print("We can also format a string in this way:")
    collection = secret_formula(start_point)
    # this is an easy way to apply a list to a format string
    print("We'd have {} beans, {} jars, and {} crates.".format(*collection))
    '''
    With a starting point of: 10000
    We can also format a string in this way:
    We'd have 5000000 beans, 5000.0 jars, and 50.0 crates.
    '''
    ######################将自定义函数作为模块,下面是ex25.py模块
    def break_words(stuff):
        """This function will break up words for us."""
        words = stuff.split(' ')
        return words
    
    def sort_words(words):
        """Sorts the words."""
        return sorted(words)
    
    def print_first_word(words):
        """Prints the first word after popping it off."""
        word = words.pop(0)#pop() 函数用于移除列表中的一个元素,默认删除最后一个列表值
        print(word)
    
    def print_last_word(words):
        """Prints the last word after popping it off."""
        word = words.pop(-1)
        print(word)
    
    def sort_sentence(sentence):
        """Takes in a full sentence and returns the sorted words"""
        words = break_words(sentence)
        return sort_words(words)
    
    def print_first_and_last(sentence):
        """Prints the first and last words of the sentence."""
        words = break_words(sentence)
        print_first_word(words)
        print_last_word(words)
    
    def print_first_and_last_sorted(sentence):
        """Sorts the words then prints the first and last one."""
        words = sort_sentence(sentence)
        print_first_word(words)
        print_last_word(words)
    /调用模块
    import ex25#输入import ex25.py 时会收到错误。不要在后面加 .py 
    sentence = "All good things come to those who wait."
    words = ex25.break_words(sentence)
    words
    sorted_words = ex25.sort_words(words)
    sorted_words
    ex25.print_first_word(words)
    ex25.print_last_word(words)
    words
    ex25.print_first_word(sorted_words)
    ex25.print_last_word(sorted_words)
    sorted_words
    sorted_words = ex25.sort_sentence(sentence)
    sorted_words
    ex25.print_first_and_last(sentence)
    ex25.print_first_and_last_sorted(sentence)
    ###################如果感觉输入太多ex25.,可以作如下更改
    import ex25
    from ex25 import *
    print_first_and_last_sorted(sentence)#不用使用ex25.print_first_and_last_sorted(sentence)
    #运行help(ex25)和help(ex25.break_words)。注意你是如何获取到关于这个模块的帮助的，
    #以及帮助是如何放在 ex25 的每一个函数后面的 """ 字符串里的。
    
    ############if-else语句#####################
    '''
    Python 一般会让你在一个带 ： 的代码行下面缩进四个空格来表示这个代码块。
    '''
    if cars > people:
        print("We should take the cars.")
    elif cars < people:
       print("We should not take the cars.")
    else:
       print("We can't decide.")
    
    #################for循环
    #列表:以左方括号（ [ ）开始打开列表，然后把你想要的条目用逗号隔开放进去，最后用右方括号（ ] ）来表明列表的结束。就是一个按顺序从头到尾组成的容器. 列表的第一个元素是从序号 0 开始，而不是从 1 开始
    #如何如何创建一个二维列表？可以用这种列表中的列表：[[1,2,3],[4,5,6]]
    # for-loop  可以用一个没有被定义的变量
    # we define a list
    change = [1, 'pennies', 2, 'dimes', 3, 'quarters']
    
    # we can also build lists, first start with an empty one
    elements = []
    
    # range(0, 3)表示的是0,1,2.没有3.
    for i in range(0, 3):
        print(f"Adding {i} to the list.")
        elements.append(i) # append在列表末尾添加新的对象
    
    # now we can print them out too
    for i in elements:
        print(f"Element was: {i}")
    	
    for i in change:
        print(f"Adding {i} to the list.")
        elements.append(i) # append在列表末尾添加新的对象	
    	
    # now we can print them out again
    for i in elements:
        print(f"Element was: {i}")	
    '''
    Adding 0 to the list.
    Adding 1 to the list.
    Adding 2 to the list.
    Element was: 0
    Element was: 1
    Element was: 2
    Adding 1 to the list.
    Adding pennies to the list.
    Adding 2 to the list.
    Adding dimes to the list.
    Adding 3 to the list.
    Adding quarters to the list.
    Element was: 0
    Element was: 1
    Element was: 2
    Element was: 1
    Element was: pennies
    Element was: 2
    Element was: dimes
    Element was: 3
    Element was: quarters
    '''
    ###################while循环
    i = 0 
    numbers = [] 
    
    while i < 6: 
        print(f"At the top i is {i}") 
        numbers.append(i) 
    
        i = i + 1 
        print("Numbers now: ", numbers) 
        print(f"At the bottom i is {i}") 
    
    
    print("The numbers: ") 
    
    for num in numbers: 
        print(num) 
    #################################综合if while for
    '''
    一些建议:
    1. 只有在循环永不停止时使用“while循环”，这意味着你可能永远都用不到。这条只有
    Python 中成立，其他的语言另当别论。
    2. 其他类型的循环都使用“for循环”，尤其是在循环的对象数量固定或者有限的情况
    下。
    1. 每一个“if 语句”必须包含一个 else。
    2. 如果这个 else 永远都不应该被执行到，因为它本身没有任何意义，那你必须在 else
    语句后面使用一个终止函数,如下例叫做 dead 的函数，让它打印出错误信息并且终止，按照这个思路你可以找到很多错误。
    3. “if 语句”的嵌套不要超过 2 层，最好尽量保持只有 1 层。
    4. 最好的调试程序的方法是用 print 在每个你想要检查的关键环节将关键变量打印出来，从而检查那里是否有错。
    '''
    from sys import exit 
    
    def gold_room(): 
        print("This room is full of gold. How much do you take?") 
    
        choice = input("> ")  # input() 函数接受一个标准输入数据，返回的永远都是string 类型。可以float(input())变为数字类型
        '''
    	 #if..in和if..not in语句,三种情况:
    	 1,If it's a string (as in your example), then in checks for substrings.
    	 2,If it's a different kind of iterable (list, tuple, set...), then in checks for membership.
    	 3,In a dictionary, in checks only for keys, never for values.
    	'''
        if "0" in choice or "1" in choice:   ##输入20和51的结果一样,输入55的结果不一样,因为55没有0或1
            how_much = int(choice)   
        else: 
            dead("Man, you should type a number contain 0 or 1.") 
    
        if how_much < 50: 
            print("Nice, you're not greedy, you win!") 
            exit(0)  #程序可以用 exit(0) 来结束，其中传入的数字代表是否有错误。如果你用 exit(1) 代表有 1 个错误， exit(0) 则代表程序正常退出。
        else: 
            dead("You greedy bastard!")
    
    def bear_room():
        print("There is a bear here.")
        print("The bear has a bunch of honey.")
        print("The fat bear is in front of another door.")
        print("How are you going to move the bear?")
        bear_moved = False
    
        while True:       #构建一个无限循环
            choice = input("> ")
    
            if choice == "take honey":
                dead("The bear looks at you then slaps your face")
            elif choice == "taunt bear" and not bear_moved:
                print("The bear has moved from the door.")
                print("You can go through it now.")
                bear_moved = True
            elif choice == "taunt bear" and bear_moved:
                dead("The bear gets pissed off and chews your leg.")
            elif choice == "open door" and bear_moved:
                gold_room()
            else:
                print("I got no idea what that means.")
    		
    def dead(why): 
        print(why, "Bye!") 
        exit(0) 
    
    def start(): 
        print("You are in a dark room.") 
        print("There is a door to your right and left.") 
        print("Which one do you take?") 
    
        choice = input("> ") 
    
        if choice == "left": 
            bear_room() 
        elif choice == "right": 
            dead("You get wrong direction.")  
        else: 
            dead("You stumble around the room until you starve.") 
    
    
    start()

#######################################列表处理, 列表是有顺序的,for 循环经常使用列表
    ten_things = "Apples Oranges Crows" 
    print("Wait there are not 5 things in that list. Let's fix it.") 
    
    stuff = ten_things.split(' ') 
    more_stuff = ["Banana", "Girl", "Boy"] 
    
    while len(stuff) != 5: 
        next_one = more_stuff.pop() #移除最后一个元素
        print("Adding: ", next_one) 
        stuff.append(next_one) 
        print(f"There are {len(stuff)} items now.") 
    
    print("There we go: ", stuff) 
    
    print("Let's do some things with stuff.") 
    
    print(stuff[1]) 
    print(stuff[-1]) #取最后一个元素
    print(stuff.pop()) 
    print(' '.join(stuff)) #用空格把stuff里的元素连接起来
    print('#'.join(stuff[1:4])) # 用空格把stuff里的1-3元素连接起来,不包含4.
    '''
    Wait there are not 5 things in that list. Let's fix it.
    Adding:  Boy
    There are 4 items now.
    Adding:  Girl
    There are 5 items now.
    There we go:  ['Apples', 'Oranges', 'Crows', 'Boy', 'Girl']
    Let's do some things with stuff.
    Oranges
    Girl
    Girl
    Apples Oranges Crows Boy
    Oranges#Crows#Boy
    '''
    ##################################################################字典
    stuff = {'name': 'Zed', 'age': 39, 'height': 6 * 12 + 2}
    print(stuff['height'])
    stuff['city'] = "SF"
    print(stuff['city'])
    stuff[2] = "Neato"
    print(stuff)
    del stuff['age']
    del stuff[2]
    print("after del: ",stuff)
    '''
    74
    SF
    {'name': 'Zed', 'age': 39, 'height': 74, 'city': 'SF', 2: 'Neato'}
    after del:  {'name': 'Zed', 'height': 74, 'city': 'SF'}
    '''
    ###########################################################字典的使用
    # create a mapping of state to abbreviation
    states = {
        'Florida': 'FL',
        'California': 'CA',
        'Michigan': 'MI'
    }
    
     # create a basic set of states and some cities in them
    cities = {
        'CA': 'San Francisco',
        'MI': 'Detroit',
        'FL': 'Jacksonville'
     }
    print("Michigan has: ", cities[states['Michigan']]) 
    '''
    items() 方法把字典中每对 key 和 value 组成一个元组，并把这些元组放在列表中返回。
    d = {'one': 1, 'two': 2, 'three': 3}
    >>> d.items()
    dict_items([('one', 1), ('two', 2), ('three', 3)])
    '''
    for state, abbrev in list(states.items()):  
        print(f"{state} state is abbreviated {abbrev}",end=',')
        print(f"and has city {cities[abbrev]}")
    
    state = states.get('Texas')
    if not state:
        print("Sorry, no Texas.")
    
    # get a city with a default value
    city = cities.get('TX', 'Does Not Exist') #返回指定 键 的值，如果键不在字典中返回默认值 None 或者设置的默认值(这里设定的是Does Not Exist)。
    print(f"The city for the state 'TX' is: {city}")	
    '''
    Michigan has:  Detroit
    Florida state is abbreviated FL,and has city Jacksonville
    California state is abbreviated CA,and has city San Francisco
    Michigan state is abbreviated MI,and has city Detroit
    Sorry, no Texas.
    The city for the state 'TX' is: Does Not Exist
    '''
    ###################################################模块
    '''
    1. 一个包含函数和变量的 Python 文件 ..
    2. 你导入这个文件。
    3. 你用 . 运算符来获取这个模块中的函数或变量。
    
    建立一个模块mystuff.py:
    1  def apple(): 
    2      print("I AM APPLES!") 
    3 
    4  # this is just a variable 
    5  tangerine = "Living reflection of a dream"
    使用模块:
    1        import mystuff
    2
    3        mystuff.apple()
    4        print(mystuff.tangerine)
    
    '''
    ###################################################类
    '''
    1  class MyStuff(object): 
    2 
    3      def __init__ (self): 
    4          self.tangerine = "And now a thousand years between" 
    5 
    6      def apple(self): 
    7          print("I AM CLASSY APPLES!")
    '''
    '''
    如果说类是一个小型模块，那么应该要有一个概念和 import 类似。这个概念就叫做“实例化”
    （instantiate），你可以理解为它是“创造”（create）一词的华而不实、令人讨厌、自以为是的说法。当
    你实例化一个类时，你所得到的东西就叫做对象(object)。然后你必须把对象赋给一个变量来使用。
    '''
    '''
    模块和类使用的区别
    4  # module style 
    5  mystuff.apples() 
    6  print(mystuff.tangerine) 
    7 
    8  # class style 
    9   thing = MyStuff()  #必须把对象赋给一个变量来使用
    10  thing.apples()    
    11  print(thing.tangerine)
    '''
    
    # create a basic set of states and some cities in them
    class Song(object):
        def __init__(self, lyrics):
            self.lyrics = lyrics
    
        def sing_me_a_song(self):
            for line in self.lyrics:
                print(line)
    
    happy_bday = Song(["Happy birthday to you",
                       "I don't want to get sued",
                       "So I'll stop right there"])  #这里self就是happy_bday
    
    bulls_on_parade = Song(["They rally around tha family",
                            "With pockets full of shells"])  #这里self就是bulls_on_parade
    
    happy_bday.sing_me_a_song()
    
    bulls_on_parade.sing_me_a_song()
    
    '''
    Happy birthday to you
    I don't want to get sued
    So I'll stop right there
    They rally around tha family
    With pockets full of shells
    '''
    
    ############################################类中的_init_
    '''
    注意到__init__方法的第一个参数永远是self，表示创建的实例本身，因此，在__init__方法内部，就可以把各种属性绑定到self，因为self就指向创建的实例本身。
    有了__init__方法，在创建实例的时候，就不能传入空的参数了，必须传入与__init__方法匹配的参数，但self不需要传，Python解释器自己会把实例变量传进去
    '''
    class Person:
        def __init__(self, name):
            self.name = name
        def say_hi(self):
            print('Hello, my name is', self.name)
    
    p = Person('Swaroop')  #这里不可以p = Person() ;必须实例化时带参数'Swaroop'
    p.say_hi()
    # 前面两行同时也能写作
    # Person('Swaroop').say_hi()

# python查找表: #

lambda作为一个表达式，定义了一个匿名函数，如

lambda x,y:x+y

上例的代码冒号前的x和y为函数参数，冒号后的x+y为函数体.返回值就是计算结果.

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