Python编程——循环语句（for、while和嵌套循环的用法详解）

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for i in 一组值：          #一组值可以是除数字以外的基本类型
	要执行的操作

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#for循环遍历字符串
str='abc'
for i in str:
	print(i)

结果如下：
a
b
c

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tup1=(31,29,31,30,31,30,31,31,30,31,30,31)
for i in tup1:
    print(i,end=' ')   #end=' ' 不换行
 
结果如下:
31 29 31 30 31 30 31 31 30 31 30 31

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Fruits=['apple','orange','banana','grape']
for fruit in Fruits:
    print(fruit)
 
结果如下:
apple
orange
banana
grape

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set1={'lisi',180,60,99}    
for i in set1:
    print(i)
 
结果如下:
lisi
99
180
60

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dict1={'name':'lisi','height':180,'weight':60,'score':99}
for k,v in dict1.items():    #遍历字典dict1中的键值对  
    print(k,'--->',v)
print('--------------')  
for k in dict1.keys():       #遍历字典dict1中所有的键
    print(k)
print('--------------')     
for v in dict1.values():     #遍历字典dict1中所有的值 
    print(v)
 
结果如下:
name ---> lisi
height ---> 180
weight ---> 60
score ---> 99
--------------
name
height
weight
score
--------------
lisi
180
60
99

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for content in open("1.txt"):   #当前目录下的1.txt
    print(content)
 
结果如下:
朝辞白帝彩云间，千里江陵一日还。
 
 
 
两岸猿声啼不住，轻舟已过万重山。

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sum = 1
for i in list(range(1,10)):   #range序列含左不含右
    sum *= i
print("1*2...*9 =",sum)
 
结果如下:
1*2...*9 = 362880

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fruits = ['banana','apple','mango','grape']
for index in range(len(fruits)):
   print('当前水果 :', fruits[index])
 
结果如下:
当前水果 : banana
当前水果 : apple
当前水果 : mango
当前水果 : grape

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while  判断条件：        #判断条件boolean类型的表达式
	执行语句

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n=1
sum=0
while n <= 100:
    if n%2==0:
       sum += n
    n=n+1
print('1到100的偶数和为:',sum)
 
结果如下:
1到100的偶数和为: 2550

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n=1
bei3_5=[]
bei3=[]
bei5=[]
while n<=100:
    if (n%3==0)and(n%5==0):
        bei3_5.append(n)
    elif n%3==0:
        bei3.append(n)
    elif n%5==0:
        bei5.append(n)
    n=n+1
else:                                     #while...else 在条件语句为false时执行else块
    print('1-100内是3和5的倍数有:',bei3_5)
    print('1-100内是3的倍数有:',bei3)
    print('1-100内是5的倍数有:',bei5)
    print('循环结束')
 
结果如下:
1-100内是3和5的倍数有: [15, 30, 45, 60, 75, 90]
1-100内是3的倍数有: [3, 6, 9, 12, 18, 21, 24, 27, 33, 36, 39, 42, 48, 51, 54, 57, 63, 66, 69, 72, 78, 81, 84, 87, 93, 96, 99]
1-100内是5的倍数有: [5, 10, 20, 25, 35, 40, 50, 55, 65, 70, 80, 85, 95, 100]
循环结束

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for i in range(1,10):
    for j in range(1,i+1):
        print(j,'*',i,'=',(j*i),end='t')
    print()

结果如下:
1 * 1 = 1
2 * 1 = 2       2 * 2 = 4
3 * 1 = 3       3 * 2 = 6       3 * 3 = 9
4 * 1 = 4       4 * 2 = 8       4 * 3 = 12      4 * 4 = 16
5 * 1 = 5       5 * 2 = 10      5 * 3 = 15      5 * 4 = 20      5 * 5 = 25
6 * 1 = 6       6 * 2 = 12      6 * 3 = 18      6 * 4 = 24      6 * 5 = 30      6 * 6 = 36
7 * 1 = 7       7 * 2 = 14      7 * 3 = 21      7 * 4 = 28      7 * 5 = 35      7 * 6 = 42      7 * 7 = 49
8 * 1 = 8       8 * 2 = 16      8 * 3 = 24      8 * 4 = 32      8 * 5 = 40      8 * 6 = 48      8 * 7 = 56      8 * 8 = 64
9 * 1 = 9       9 * 2 = 18      9 * 3 = 27      9 * 4 = 36      9 * 5 = 45      9 * 6 = 54      9 * 7 = 63      9 * 8 = 72      9 * 9 = 81