python 列表解析

列表解析函数式：
[expr for iter_var in iterable]
[expr for iter_var in iterable if cond_expr]

exp：
1.
>>> seq = [11,10,9,9,5,35,8,20,31,72,54,53]
>>> [x for x in seq if x%2]
 [11, 9, 9, 5, 35, 31, 53]
2.
>>> [(x+1,y+1) for x in range(3) for y in range(5)]
[(1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (2, 1), (2, 2), (2, 3), (2, 4), (2, 5), (3, 1), (3, 2), (3, 3), (3, 4), (3, 5)]
>>> [(x,y) for x in range(3) for y in range(3)]
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]
3.经典例子
>>> books=[ 
　　　　　　　{"name":u"C#从入门到精通","price":23.7,"store":u"卓越"}, 
　　　　　　　{"name":u"ASP.NET高级编程","price":44.5,"store":u"卓越"}, 
　　　　　　　{"name":u"Python核心编程","price":24.7,"store":u"当当"}, 
　　　　　　　{"name":u"JavaScript大全","price":45.7,"store":u"当当"}, 
　　　　　　　{"name":u"Django简明教程","price":26.7,"store":u"新华书店"}, 
　　　　　　　{"name":u"深入Python","price":55.7,"store":u"新华书店"}, 
　　　　　　]
# 列表中价格最低的书目
#原始方法：
>>> price=[]
>>> for item in books:
    for p in item:
        if p == 'price':
            price.append(item[p])
>>> min(price)
23.699999999999999

#列表解析：
>>> min([item[p] for item in books for p in item if p=='price'])
23.699999999999999

#Python相关书籍检索
# 原始方法：
for item in books: 
　　for p in item: 
　　　　if item['name'].find('Python')>=0: 
　　　　　　print item[p],#24.7 Python核心编程 当当 55.7 深入Python 新华书店  

#列表解析
total = [item[p] for item in books for p in item if item['name'].find('Python')>=0] 
print total #[24.699999999999999, u'Python\u6838\u5fc3\u7f16\u7a0b', u'\u5f53\u5f53', 55.700000000000003, u'\u6df1\u5165Python', u'\u65b0\u534e\u4e66\u5e97']

此博客转载自：http://www.cnblogs.com/BeginMan/p/3164937.html