# 条件判断

``````if False:
print("True")
else:
print("False")
print("end")``````

python指定任何非0和非空值为True,0或None为False

``````score = 87

if score>=90 and score <=100:
print("本次考试·等级为A")
elif score >=80 and score <90:
print("本次考试·等级为B")
elif score >=70 and score <80:
print("本次考试·等级为C")
elif score >=0 and score <60:
#else:                 #else和elif一起使用
print("本次考试·等级为E")``````

if 条件（and条件）：elif条件：else：

``````xingbie = 1  #1代表男生，0代表女生
danshen = 1  #1代表单身，0代表有对象

if xingbie == 1 :
print("男生")
if danshen == 1:
print("我给你介绍一个吧？")
else:
print("你给我介绍一个吧")
else:
print("女生")
print(".....")``````

“套娃”

``````import random   #引入随机库
x= random.randint(0,2)      #随机生成（0，2）的随机数，包括0，1，2三个数字

print(x)``````

``````#课堂练习
import random
x = random.randint(0,2)
print("随机生成数字为：",x)
print("你的输入为：剪刀（0）")
print("你的输入为：石头（1）")
else:
print("你的输入为：布（2）")

print("平局")
print("哈哈，你输了：）")
elif password ==1 and x ==2:
print("哈哈，你输了：）")
else:
print("恭喜你赢啦！")``````

# 循环语句

``````for i in range(5):
print(i)``````

range也可以换成name、len(a)。（5）是指从0、1、2、3、4。

``````for i in range(0,13,3):   #从0开始，到13结束，步进值为3
print(i)``````

（1，2，3）1指开始，2指结束，3指步进值。

``````for i in range (-10,-100,-30):
print(i)``````

负数也可以

``````name = "chengdu"

for x in name:
print(x,end="\t")``````

``````a = ["aa","bb","cc","dd"]
for i in range(len(a)):
print(i,a[i])``````

a[i]指a列表里第i个元素

``````i = 0
while i <5:
print("当前是第%d次执行循环"%(i+1))
print("i=%d"%i)
i += 1
``````

课堂练习之1-100求和

``````#1-100求和
n = 100
sum = 0
counter = 1
while counter <= n:
sum = sum+counter
counter += 1

print("1到%d的和为：%d"%(n,sum))``````

``````count=0
while count<5:
print(count,"小于5")
count +=1
else:
print(count,"大于等于5")``````

``````i=0
while i<10:
i=i+1
print("-"*30)
if i==5:
break    #结束整个while循环
print(i)``````

break结束整个while循环

``````i=1
while i<10:
i=i+1
print("-"*30)
if i==5:
continue  #结束本次循环
print(i)``````

continue结束套娃里的本次循环

``````for i in range(1,10):
for j in range (1,i+1):
print('%d*%d=%d\t'%(j,i,i*j),end='')
print('')``````
``````i=1
j=1
while i<10:
while j<(i+1):
print('%d*%d=%d'%(j,i,i*j),end="\t")
j=j+1
print()
i+=1
j=1
``````