04 if语句与循环语句

if语句

单一结构

age=32
if age<=6:
    print("童年")
else:
    print("非童年")

复合结构

if age<=6:
    print("童年")
elif age<=18:
    print("少年")
elif age<=41:
    print("青年")
elif age<=66:
    print("中年")
else:
    print("老年")

元素是否在集合中

v=10
a=[1,2,3,4,5,6,7]
if v in a:
    print("在")
else:
    print("不在")

循环语句

for循环

alist = (1,2,3,4,5)
for item in alist:
    print(item)

blist = [1,2,3,4,5,6]
for item in blist:
    print(item)

while循环

print("=========================")
clist = [6,7,8,9,10]
i=0
while i<len(clist):
    print(clist[i])
    i=i+1

嵌套循环

print("=========================")
dlist = [[1,2,3],[4,5,6],[7,8,9]]
n=0
for lst in dlist:
    for item in lst:
        n=n+item
print("累加结果:",n)

break语句

结束循环

continue语句

跳出本次循环

列表推导式

通过列表推导式生成一个集合

[i for i in range(1,51) if i%2==0]
[表达式  for表达式  for表达式或if表达式]
输出结果：
[2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50]