python中filter, map, reduce, lambda

#!/usr/bin/env python
#_*_coding:utf-8_*_


#filter(function, sequence)：
#对sequence中的item依次执行function(item)，将执行结果为True的item组成一个List/String/Tuple（取决于sequence的类型）返回。
#可以看作是过滤函数。
tasks = [
    {
        ‘id‘: 1,
        ‘title‘: u‘golang‘,
        ‘description‘: u‘Golang‘, 
        ‘done‘: False
    },
    {
        ‘id‘: 2,
        ‘title‘: u‘Learn Python‘,
        ‘description‘: u‘Need to find a good Python tutorial on the web‘, 
        ‘done‘: False
    }
]

def get_task(task_id):
    task = filter(lambda t: t[‘id‘] == task_id, tasks)
    print task

get_task(2)


# map(function, sequence) 
# 对sequence中的item依次执行function(item)，执行结果组成一个List返回
def add(x, y):
    return x + y

print map(add, range(10), range(10))
print map(lambda x,y:x+y, range(10), range(10))

def _str(s):
    s = s + ".log"
    return s

s = ["a", "b", "c"]
print map(_str, s)

#reduce(function, sequence, starting_value)
#对sequence中的item顺序迭代调用function，如果有starting_value，还可以作为初始值调用，例如可以用来对List求和
print reduce(add, range(1, 10))

[{‘description‘: u‘Need to find a good Python tutorial on the web‘, ‘done‘: False, ‘id‘: 2, ‘title‘: u‘Learn Python‘}]
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
[‘a.log‘, ‘b.log‘, ‘c.log‘]
45