python lambda reduce yield isinstance

lambda:　

>>> f=lambda x,y,z:x+y+z
>>> f(1,2,3)
6
>>> f=lambda x,y,z:x+y+x
>>> f(1,2,3)
4
>>> 
>>> n=5
>>> reduce(lambda x,y:x*y,range(1,n+1))
120
>>> 
>>> def action(x):
...     return lambda y:x+y
... 
>>> a=action(2)
>>> a(22)
24
>>> b=lambda x:lambda y:x+y
>>> a=b(3)
>>> a(2)
5
>>> (b(2))(2)
4
>>> 
>>> 
>>> n = 5
>>> print reduce(lambda x, y: x * y, range(1, n + 1))
120
>>> 
>>> m = 2
>>> n = 5
>>> print reduce( lambda x, y: x * y, range( 1, n + 1 ), m )  # 240
240

>>> map( lambda x: x*x, [y for y in range(10)] )
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

reduce:

## reduce(f, [x1, x2, x3, x4]) = f(f(f(x1, x2), x3), x4)

>>> def add(x, y):
...     return x + y
... 
>>> reduce(add, [1, 3, 5, 7, 9])
25

yield:

## yield 解释器会将其视为一个 generator 返回一个 iterable 对象

>>> def fab(max): 
...     n, a, b = 0, 0, 1 
...     while n < max: 
...         yield b 
...         # print b 
...         a, b = b, a + b 
...         n = n + 1 
... 
>>> for n in fab(5):
...     print n
... 
1
1
2
3
5

def _filter_one(obj, spec_obj):
    return True

def filter_all(filter_obj_list, spec_obj):
    for obj in filter_obj_list:
        if _filter_one(obj, spec_obj):
            yield obj

filter_obj_list=[1,2,3]
spec_obj=None

print list(filter_all(filter_obj_list,spec_obj))

# python test.py
[1, 2, 3]

isinstance:

#推荐实用判断type的时候实用isinstance而非type，理由如下，自定义的type判断可能不准确

>>> class A():
...     pass
... 
>>> class B():
...     pass
... 
>>> a = A()
>>> b = B()
>>> print(type(a) is type(b))
True
>>> print(isinstance(type(a),type(b)))
False