python中if语句的练习

蔚落 2021-12-23 07:15 519阅读 0赞

## 1.if条件判断 ##

if 要判断的条件：  
条件成立的时候做的事情

age = 7
    
    if age >= 7:
        print('欢迎进入小学...')
    
    print('请回幼儿园！')

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70]

## 2.if-else ##

if 要判断的条件：  
条件成立的时候做的事情  
else:  
条件不成立的时候做的事情

age = 2
    
    if age >= 7:
        print('欢迎进入小学...')
    else:
        print('请回幼儿园！')

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 1]

## 3.if逻辑运算符 ##

and  
条件1 and 条件2  
两个条件都满足，就返回True  
两个条件有一个不满足，返回False

or  
条件1 or 条件2  
两个条件只要有一个满足，就返回True  
两个条件都不满足，返回False

age = 100
    if age >= 0 and age <=100:
        print('年龄正确')
    else:
        print('年龄错误')age = 100

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 2]

age = 100
    if age >= 0 or age <=100:
        print('年龄错误')
    else:
        print('年龄正确')

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 3]

a = input('Num:')
    # if a == '':
    #     print('请输入合法的值！')
    if not a:
        print('请输入合法的值！')

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 4]![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 5]

## 5.if嵌套 ##

格式：  
if 条件1:  
条件1满足执行的动作  
if 满足条件1的基础上的条件2:  
…  
else:  
条件2不满足的情况下  
else:  
条件1不满足时，执行的动作

ticket = False/True
    
    knife = 16
    
    if ticket:
        print('车票检查通过，请安检')
        if knife > 15:
            print('长度为 %d:超出限定长度，无法入内' %knife)
        else:
            print('长度为 %d:限定长度内，允许入内' %knife)
    else:
        print('请买票')

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 6]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 7]  
**练习：**  
1. 输入年、月，输出本月有多少天。合理选择分支语句完成设计任务。  
输入样例1：2004 2  
输出结果1：本月29天  
输入样例2：2010 4  
输出结果2：本月30天

year = int(input('Year:'))
    month = int(input('Month:'))
    
    if (month == 1 or month == 3 or month == 5 or month == 7
        or month == 8 or month == 10 or month == 12):
        print('31天')
    elif (month == 4 or month == 6 or month == 9 or month == 11 ):
        print('30天')
    elif month == 2 and ((year % 4==0 and year % 100!=0) or (year % 400==0)):
        print('29天')
    else:
        print('28天')

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 8]  
在shell中可以输入cal+年份，来查看日历  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 9]

2.从控制台输入要出的拳 —石头(1)/剪刀(2)/布(3)；电脑随即出拳–先假定电脑只会出石头，完成整体代码功能；比较胜负

import random
    #1.用户出拳
    player = input('请输入你要出的：石头（1）剪刀（2）布（3）：')
    #2.电脑出拳
    computer = random.randint(1,3)
    #3.比较胜负
    if ((player == 1 and computer == 2) \
            or (player == 2 and computer == 3)\
            or (player == 3 and computer == 1)):
        print('玩家赢')
    elif player == computer:
        print('平局')
    else:
        print('玩家输')

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 10]

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