循环语句

循环语句

• python有两种循环，一种是for循环；

names = ['Michael','Bob','Tracy']
for name in names:
    print (name)

Michael
Bob
Tracy

• for x in ... 把每一个元素循环带入给x,然后执行缩进快的语句；

range(5)

range(0, 5)

sum = 0
for x in [1,2,3,4,5,6,7,8,9]:
    sum = x + sum
print (sum)

45

如果计算1-100之间的和，需要由range()函数，可以生成一个整数序列，在通过list()函数可以转换成list;

list(range(5))

[0, 1, 2, 3, 4]

for x in range(5):
    print (x)
    

0
1
2
3
4

• 计算1..100相加

sum = 0
for x in range(101):
    sum += x
print (sum)

5050

sum = 0
for x in range(101):
    sum = x + sum
print (sum)

5050

• 另一种循环，while循环，计算奇数之和

sum = 0 
n = 99
while n > 0:
    sum += n
    n = n - 2
print(sum)

2500

• 计算1..100的和

sum = 0
n = 100
while n > 0:
    sum = n + sum
    n = n - 1
print (sum)

5050

• break,退出

n = 1
while n <= 100:
    print(n)
    n += 1
print('END')

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END

n = 1
while n <= 100:
    if n > 10:
        break
    print (n)
    n = n + 1
print ('END')
    

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END

• continue ,再循环过程中跳出当前循环，直接开始下一个循环

n = 0
while n < 10:
    n = n + 1
    if n % 2 == 0:
        continue
    print (n)

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