循环

循环

for 循环

range左闭右开

省略最后一个参数

def sum(n):
	total=0
	for x in range(n+1):
		tltal+=x
	return total#range默认起始为0

添加第三个参数（步长

def sum(m,n,k)
	for i in range(1,10,2)
	print(i)

0 2 4 6 8

只对m到n奇数求和

def sum(m,n):
	total =0
	for x in range(m,n+1):
		if x%2==1:
			total+=x
	return total

sum(4,10)===(5+7+9)

for i in range(10,0,-1)
	print(i)

10 9 8 7 6 5 4 3 2 1

def pmy(n):
	for i in range(n):
	print(i,end=" ")
	for x in range(x):
		print("*",end=" ")
	print()
pmy(5)

0

1 *

2 * *

3 * * *

4* * * *

while循环

不知道循环什么时候停

def id(n):
	n=abs(n)
	while n>=10:
		n=n//10
	return n
id(-79)

7

依次找出n个4或7的整数倍

def isM(x):
	return((x%4)==0）or((x%7)==0)
def nthM(n):
	found=0
	guess=-1
	while found<=n:
		guess+=1
		isM(guess):
			found+=1
	return n
print("倍数"，end="")
for n in range(15):#找15个
	print(nthM(n),end="")
	

break与continue

for i in range(200):
	if n%3==0:
		continue#跳过这个循环
	elif n==8:
		break#跳出当前整个循环
	else:
		pass#啥也不做
	print(n,end="")

1 2 4 5 7

假-死循环

练习

判断质数

慢

isPrime(n):
	if n<2:
		return False
	for i in range(2,n):
		if n%i==0:
			retuen False
	return True

快

def isprime(n):
	if n<2:
		return False
	if n==2:
		return True
	if n%2==0:
		return  False
	max=round(n**0.5)
	for f in range(3,max+1,2):
		if n%f==0:
			return False
	return True