1.0 if 判断

if  4 > 5:
  print('我请你喝酒')
else:
  print('我请你吃饭')

多级判断

num = input('请输入你猜的数字: ')
#input 输入的是字符串，所以数字要要加''
if  num == '1':
  print('一起抽烟')
elif num == '2':
  print('一起喝酒')
elif num == '3':
  print('一起吃饭')
else:
  print('各回各家')

案例3

score = int(input("请输入分数:"))
if score > 100:
  print("我擦，最高才100.。。")
elif score >= 90:
  print("A")
elif score >= 80:
  print("B")
elif score >= 60:
  print('C')
elif score >= 40:
  print('D')
else:
  print('太笨了')

2.0 while 循环的应用

案例一打印1~100

count = 1
flag = True                #满足条件，执行循环
while flag:
    print(count)
    count = count + 1
    if   count  > 100:
           flag = False     #False 退出循环

第二种方法

count = 1
while count  <= 100:            #在循环的时候就指定条件
        print(count)
        count =  count + 1

案例二打印1+2+3~+100

count = 1
sum = 0
while count <= 100:
      sum = sum + count
      count = count + 1
print(sum)

3.0跳出循环---------------break

count = 1
while True:
    print(count)
    count = count + 1 
    if count > 200:
        break     #当count > 200时跳出循环

利用 break 打印1~100

count = 1 
while True:
     print(count)
     count =  count + 1
     if count > 100:
          break

4.0 结束本次循环，开始下次循环---------------continue

print(111)
count = 1
while count < 20:
  print(count)
  continue
  count = count + 1

案例一:打印1，2，3，4，5，6，8，9，10

count = 0
while  count <= 9:
    count = count + 1
    if  count == 7:
        continue
    print(count)