[i for i in range(100)]       #列表解析

g = (i for i in range(1000))    #生成器表达式     #不用yield的表达形式

print(g)  #这是一个迭代对象

print(next(g))    #next(g) == g.__next__()    #next(g)相当于g.__next__()

print(next(g))    #next(g) == g.__next__()

print(next(g))    #next(g) == g.__next__()

print(next(g))    #next(g) == g.__next__()

print(next(g))    #next(g) == g.__next__()

# 列表解析

l = []

with open('goods', encoding='utf-8') as f:

    l = [float(line.split()[1]) * int(line.split()[2]) for line in f]

    print(sum(l))

# 生成器表达式

with open('goods', encoding='utf-8') as f:

    g = (float(line.split()[1]) * int(line.split()[2]) for line in f)

    print(sum(g))

# 换个方式

g = (float(line.split()[1]) * int(line.split()[2]) for line in open('goods', encoding='utf-8'))

print(sum(g))