4.python的基础语法元素_控制流程

心已赠人 2023-06-23 14:25 39阅读 0赞

#-*- coding: utf-8 -*-
    
    print ("===========条件测试==========")
    #比较运算
    a = 10
    b = 8
    print (a>b) #大于
    print (a<b) #小于
    print (a >= b)#大于等于
    print (a <= b)#小于等于
    print (a==b)
    print (a != b)
    #非空判断
    ls = [1]
    if ls:   #数据结构不为空、变量不为0、None、False 则条件成立
        print("非空")
    else:
        print("空的")
    
    #逻辑运算 与 或 非
    a = 10
    b = 8
    c = 12
    print ((a > b)and(b > c)) #与
    print ((a > b)or(b > c)) #或
    print (not(a > b)) #非
    #复合逻辑运算的优先级 非 >  与 > 或
    print (True or True and False)
    print ((True or True) and False)
    #存在运算
    #元素in 列表/字符串
    cars = ["BYD","BMW","AUDI","TOYOTA"]
    print ("BMW" in cars)
    print ("BENZ" in cars)
    #元素 not in 列表/字符串
    print ("BMW" not in cars)
    print ("BENZ" not in cars)
    
    
    
    print ("===========分支结构 if语句===========")
    #单分支
    age = 8
    if age > 7:
        print ("孩子，你该上学了")
    
    #双分支
    age = 18
    if age > 22:
        print ("可以结婚啦")
    else:
        print ("再等等")
    
    #多分支
    age = 38
    if age < 7:
        print ("再玩两年泥巴")
    elif age < 13:
        print ("孩子，你该上初中了")
    elif age < 60:
        print ("大家都要工作")
    else:
        print ("退休了")
    #嵌套循环
    
    
    print("=========for 循环=========")
    # 循环流程 从可迭代对象中，每次取出一个元素，并进行相应对操作
    #直接迭代 -- 列表[],元组(),集合{},字符串" "
    graduates = ("李雷","韩梅梅","Jim")
    for graduate in graduates:
        print ("Congratulation,"+graduate)
    #变换迭代 -- 字典
    students = {201901:'xiaoming',201902:'xiaohong',201903:'xiaoqiang'}
    for k,v in students.items():
        print (k,v)
    for student in students.keys():
        print (student)
    #range()对象
    res = []
    for i in range(1000):
        res.append(i**2)
    print (res[:5])
    
    res = []
    for i in range(1,10,2):
        res.append(i**2)
    print (res)
    
    #循环控制  break结束整个循环
    product_scores = [89,90,99,70,67]
    i = 0
    for score in product_scores:
        if score < 75:
            i += 1
        if i == 2:
            print ("产品抽检不合格")
    #continue 结束本次循环
    product_scores = [89,90,99,70,67]
    for i in range(len(product_scores)):
        if product_scores[i] >= 75:
            continue
        print ("第{0}个产品，分数为{1},不合格".format(i,product_scores[i]))
    #for与else的配合
    #如果for循环全部执行完毕，没有被break中止，则运行else块
    product_scores = [89,90,99,70,67]
    #如果低于75分的超过2个，则该组产品不合格
    i = 0
    for score in product_scores:
        if score < 75:
            i += 1
        if i == 2:
            print ("产品抽检不合格")
            break
    else:
        print("产品抽检不合格")
    
    print("===========无限循环  while循环=========")
    i = 1
    res = 0
    while i < 5:
        res += i
        i += 1
    print (res)