python生成器表达式
生成器表达式
相比列表表达式,将[]换成了(),返回对象不是一个列表,而是一个生成器,相比列表更加省内存
实例1:
列表表达式写法:
l = ['apple%s' % i for i in range(10000)] print(l)
生成器表达式写法:
g = ('apple%s' % i for i in range(10000)) for i in g: print(i)
实例2:
一般写法:
res = [] with open('test1.txt') as f: for line in f: l = line.split(',') d = {} d['name'] = l[0] d['price'] = l[1] d['count'] = l[2] res.append(d) print(d)
生成器表达式写法:
with open('test1.txt') as f: res = (line.split(',') for line in f) dic_g = ({'name': i[0], 'price': i[1], 'count': i[2]} for i in res) apple_dic = next(dic_g) #只有调用next才会往外拿一个,大大节省内存 print(apple_dic)