第五次课课上代码

第五次

双重循环——排序（复习）

While循环

Break continue

字符串（len，取值改值，格式化）

列表生成式

>>> for i in range(4):
for j in range(4):
print(i,j)

0 0
0 1
0 2
0 3
1 0
1 1
1 2
1 3
2 0
2 1
2 2
2 3
3 0
3 1
3 2
3 3
>>> for i in range(2):
   for j in range(2):
       for k in range(2):
           print(i,j)

0 0
0 0
0 1
0 1
1 0
1 0
1 1
1 1
>>> for i in range(2):
   for j in range(2):
       for k in range(2):
           print(i,j,k)

0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
>>> for i in range(2):
   for j in range(2):
       for k in range(2):
           print(j,k)

0 0
0 1
1 0
1 1
0 0
0 1
1 0
1 1
>>> l=[4,5,7,8,2,2]
>>> for i in range(1,len(l)):#意义是第i个元素开始插入i之前的序列（已经有序）
   for j in range(i,0,-1):#只要比它之前的元素小就交换
       if l[j]<l[j-1]:
       l[j],l[j-1]=l[j-1],l[j]
       else:
       break#直到比前一个元素大

SyntaxError: inconsistent use of tabs and spaces in indentation
>>> l=[1,3,5,7,9]
>>> x=4
>>> l=[3,7,5,6,4]
>>> while x>8:
   print(x)

>>> while x<8:
   print(x)
   x=x+1

4
5
6
7
>>> while 0:
print(1)

>>> while x<8:
   print(1)
   if x>10:
       break
   x=x+1

>>> while 1:
   print(1)
   if x>10:
       break
   x=x+1

1
1
1
1
>>> l=[3,7,5,6,4]
>>> for i in range(1,len(l)):#意义是第i个元素开始插入i之前的序列（已经有序）
   for j in range(i,0,-1):#只要比它之前的元素小就交换
       if l[j]<l[j-1]:
       l[j],l[j-1]=l[j-1],l[j]
       else:
       continue#直到比前一个元素大

SyntaxError: inconsistent use of tabs and spaces in indentation
>>> for i in range(1,len(l)):#意义是第i个元素开始插入i之前的序列（已经有序）
   for j in range(i,0,-1):#只要比它之前的元素小就交换
       if l[j]<l[j-1]:
       l[j],l[j-1]=l[j-1],l[j]
       else:
       continue

SyntaxError: inconsistent use of tabs and spaces in indentation
>>> for i in range(5):
   if i%2==0:
       continue
   print(i)

1
3
>>> for i in range(100):
   if i%2==0:
       continue
   print(i,end=" ")

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99
>>> l='0123456'
>>> len(l)
7
>>> l[0]
'0'
>>> l[0]=1
Traceback (most recent call last):
File "<pyshell#48>", line 1, in <module>
l[0]=1
TypeError: 'str' object does not support item assignment
>>> l=l[:2]+'9'+l[3:]
>>> print(l)
0193456
>>> 'Hi, %s, you have $%d.' % ('Michael', 1000000)
'Hi, Michael, you have $1000000.'
>>> 'Hi, %s, you have $%5d.' % ('Michael', 5)
'Hi, Michael, you have $ 5.'
>>> 1*1=1
SyntaxError: can't assign to operator
>>> 9*9=81
SyntaxError: can't assign to operator
>>> 9*2=18
SyntaxError: can't assign to operator
9*2=18
>>> l=[0,1,2,3]
>>> l=[i for i in range(5)]
>>> print(i)
99
>>> print(l)
[0, 1, 2, 3, 4]
>>> l=[0]*10
>>> print(l)
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
>>> l=[0 for i in range(5)]
>>> print(l)
[0, 0, 0, 0, 0]
>>> l[0,1,2,3,4]
Traceback (most recent call last):
File "<pyshell#64>", line 1, in <module>
l[0,1,2,3,4]
TypeError: list indices must be integers or slices, not tuple
>>> l=[0,1,2,3,4]
>>> l=[[0],[1],[2]]
>>> l=[[0,1],[1,2],[2,3]]
>>> l[0][0]
0
>>> l[1][0]
1
>>> i=0
>>> print(i)
0
>>> l=[[0,1],[1,2],[2,3]]
>>> for i in l:
print(i)