关于ord()函数的使用、列表解析、filter()

 

 

 实际运行结果如下：

[]
>>> for x in 'span':
	res.append(ord('x'))

	
>>> res
[120, 120, 120, 120]
>>> for x in  'span':
	res.append(ord(x))

	
>>> res
[120, 120, 120, 120, 115, 112, 97, 110]
>>> 

　　

 

 这里应用对象的是序列，所以必须加[ ]

 

>>> [x **2 for x in range(10)]
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
>>> x **2 for x in range(10)
SyntaxError: invalid syntax
>>> 

　　filter的用法：

 

>>> list(lambda x:x%2 == 0)
Traceback (most recent call last):
  File "<pyshell#64>", line 1, in <module>
    list(lambda x:x%2 == 0)
TypeError: 'function' object is not iterable
>>> list(filter(lambda x: x%2 == 0,range(5)))
[0, 2, 4]

　　

>>> list(lambda x:x%2 == 0)
Traceback (most recent call last):
  File "<pyshell#64>", line 1, in <module>
    list(lambda x:x%2 == 0)
TypeError: 'function' object is not iterable
>>> list(filter(lambda x: x%2 == 0,range(5)))
[0, 2, 4]

　　

 

 1 >>> list(filter(lambda x: x%2 == 0,range(5)))
 2 [0, 2, 4]
 3 >>> list(filter(lambda:b b%2 = 0，range(101)))
 4 SyntaxError: invalid syntax
 5 >>>  list(filter(lambda b :b%2 = 0，range(101)))
 6  
 7 SyntaxError: unexpected indent
 8 >>> list(filter(lambda b :b%2 = 0，range(101)))
 9 SyntaxError: invalid character in identifier
10 >>> range(101)
11 range(0, 101)
12 >>> list(filter(lambda b :b%2 = 0, range(101)))
13 SyntaxError: expression cannot contain assignment, perhaps you meant "=="?
14 >>> list(lambda b:b %2 == 0,range(101))
15 Traceback (most recent call last):
16   File "<pyshell#71>", line 1, in <module>
17     list(lambda b:b %2 == 0,range(101))
18 TypeError: list expected at most 1 argument, got 2
19 >>> list(filter((lambda b : b% 2 ==0 ),range(101)))
20 [0, 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, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100]
21 >>>