python学习笔记8（if语句）
1.判断数值相等，不等
#if语句
colors=['red','black','white','green']
print(colors)
for color in colors[:]:
# if后面的冒号是英文状态下面的，是不可以省略的，比较数值相等用的是‘==’，不是‘=’，不相等用‘！=’，在python中cat和CAT是不同的，是区分大小写的
if color=='green':
print('I like '+color.title())#有缩进，执行多次
else:
print(color.title()+' is not my favoraite color')
print('一个元素对比结束')#没有缩进，比else高一层次，每一个元素对比完之后就执行一次
print('循环结束')
['red', 'black', 'white', 'green']
Red is not my favoraite color
一个元素对比结束
Black is not my favoraite color
一个元素对比结束
White is not my favoraite color
一个元素对比结束
I like Green
一个元素对比结束
循环结束
2.判断非空
if color:#说明对象非空
print('I like '+color.title())#有缩进，执行多次
#判断列表非空
colors=['red','black','white','green']
if colors:
print('not null')
3.判断某元素是否存在于列表中
colors=['red','black','white','green']
color='resd'
if color not in colors:#判断对象不在列表中
print(color.title()+' is not in the list')
color='red'
if color in colors:#判断对象在列表中
print(color.title()+' is in the list')
Resd is not in the list
Red is in the list
4.奶茶点单小程序
#奶茶点单小程序，由于目前所学较少，只能点一类奶茶，后期还会完善
print('*****************')
print('欢迎光临波波奶茶店,本店提供以下饮品：\n\t1.红豆相思奶茶 10元/小杯 12元/中杯 15元/大杯\n\t2.椰果珍珠奶茶 10元/小杯 12元/中杯 14元/大杯\n\t3.草莓西瓜果汁 10元/小杯 11元/中杯 12元/大杯\n\t')
milktea_number=input('请输入您想要的奶茶编号：')
if milktea_number:
milktea_number=int(milktea_number)#如果用户输入奶茶编号，就将编号记录下来
else:
milktea_number=0#默认为0，代表不点单
milktea_numbers=[]
milktea_numbers.append(milktea_number)
price=0#price参与后期计算，初值定义为0
for milktea_number in milktea_numbers[:]:
if milktea_number >= 1 and milktea_number <= 3: #注意这里的冒号（英文状态下）是不能省略的
if milktea_number == 1:
milktea_name = '红豆相思奶茶'
milktea_size = input('请输入{}号{}的规格（小杯、中杯、大杯）'.format(milktea_number,milktea_name))
if milktea_size:
milktea_size =milktea_size # 如果用户输入奶茶规格，就将规格记录下来
else:
milktea_size='大杯'#默认大杯
if milktea_size == '小杯':
milktea_price = 10#小杯价格
milktea_quantity = input('请输入奶茶数量：')
if milktea_quantity:
milktea_quantity = int(milktea_quantity) # 如果用户输入奶茶数量，就将数量记录下来
else:
milktea_quantity = 0 # 默认0杯
price += milktea_price * milktea_quantity
elif milktea_size == '中杯':
milktea_price = 12
milktea_quantity = input('请输入奶茶数量：')
if milktea_quantity:
milktea_quantity = int(milktea_quantity) # 如果用户输入奶茶数量，就将数量记录下来
else:
milktea_quantity = 0 # 默认0杯
price += milktea_price * milktea_quantity
else:
milktea_price = 15
milktea_quantity = input('请输入奶茶数量：')
if milktea_quantity:
milktea_quantity = int(milktea_quantity) # 如果用户输入奶茶数量，就将数量记录下来
else:
milktea_quantity = 0 # 默认0杯
price += milktea_price * milktea_quantity
if milktea_number == 2:
milktea_size = '大杯' # 默认大杯
milktea_name = '椰果珍珠奶茶'
milktea_size = input('请输入{}号{}的规格（小杯、中杯、大杯）'.format(milktea_number, milktea_name))
if milktea_size:
milktea_size =milktea_size # 如果用户输入奶茶规格，就将规格记录下来
else:
milktea_size='大杯'#默认大杯
if milktea_size == '小杯':
milktea_price = 10
milktea_quantity = input('请输入奶茶数量：')
if milktea_quantity:
milktea_quantity = int(milktea_quantity) # 如果用户输入奶茶数量，就将数量记录下来
else:
milktea_quantity = 0 # 默认0杯
price += milktea_price * milktea_quantity
elif milktea_size == '中杯':
milktea_price = 12
milktea_quantity = input('请输入奶茶数量：')
if milktea_quantity:
milktea_quantity = int(milktea_quantity) # 如果用户输入奶茶数量，就将数量记录下来
else:
milktea_quantity = 0 # 默认0杯
price += milktea_price * milktea_quantity
else:
milktea_price = 14
milktea_quantity = input('请输入奶茶数量：')
if milktea_quantity:
milktea_quantity = int(milktea_quantity) # 如果用户输入奶茶数量，就将数量记录下来
else:
milktea_quantity = 0 # 默认0杯
price += milktea_price * milktea_quantity
if milktea_number == 3:
milktea_size = '大杯' # 默认大杯
milktea_name = '草莓西瓜汁'
milktea_size = input('请输入{}号{}的规格（小杯、中杯、大杯）'.format(milktea_number, milktea_name))
if milktea_size:
milktea_size =milktea_size # 如果用户输入奶茶规格，就将规格记录下来
else:
milktea_size='大杯'#默认大杯
if milktea_size == '小杯':
milktea_price = 10
milktea_quantity = input('请输入奶茶数量：')
if milktea_quantity:
milktea_quantity = int(milktea_quantity) # 如果用户输入奶茶数量，就将数量记录下来
else:
milktea_quantity = 0 # 默认0杯
price += milktea_price * milktea_quantity
elif milktea_size == '中杯':
milktea_price = 11
milktea_quantity = input('请输入奶茶数量：')
if milktea_quantity:
milktea_quantity = int(milktea_quantity) # 如果用户输入奶茶数量，就将数量记录下来
else:
milktea_quantity = 0 # 默认0杯
price += milktea_price * milktea_quantity
else:
milktea_price = 12
milktea_quantity = input('请输入奶茶数量：')
if milktea_quantity:
milktea_quantity = int(milktea_quantity) # 如果用户输入奶茶数量，就将数量记录下来
else:
milktea_quantity = 0 # 默认0杯
price += milktea_price * milktea_quantity
vip = input('是否为本店会员y/n:')
if vip:
vip=vip
else:
vip='n'#默认不是会员
if vip == 'y':
price1 = price * 0.9
print(
'小主，您点了{}号{}，共{}杯{}奶茶，原计{}元，折后{}元'.format(milktea_number, milktea_name, milktea_quantity, milktea_size,price, price1))
else:
price = price
print(
'小主，您点了{}号{}，共{}杯{}奶茶，共{}元'.format(milktea_number, milktea_name, milktea_quantity, milktea_size, price))
print('小主您的奶茶已经下单，请耐心等待~')
else:
print('抱歉小主，您点的奶茶本店暂时缺货，欢迎品尝其他口味的奶茶')