TypeError: 'generator' object has no attribute '__getitem__'

Question

我写了一个应该 return 字典的生成函数。然而，当我尝试打印一个字段时，出现以下错误

print row2['SearchDate']
TypeError: 'generator' object has no attribute '__getitem__'

这是我的代码

from csv import DictReader
import pandas as pd
import numpy as np


def genSearch(SearchInfo):
    for row2 in DictReader(open(SearchInfo)):
        yield row2

train = 'minitrain.csv'

SearchInfo = 'SearchInfo.csv'

row2 = {'SearchID': -1}

for row1 in DictReader(open(train)):
    if 'SearchID' in row1 and 'SearchID' in row2 and row1['SearchID'] == row2['SearchID']:
        x = deepcopy( row1 )
        #x['SearchDate'] = row2['percent']
        x.update(row2)    
        print 'new'
        print x
    else: 
        #call your generator
        row2 = genSearch(SearchInfo)
        print row2['SearchDate']

Answer 1

生成器 returns 一个迭代器，您明确需要在其上调用 next。

你的最后一行代码应该类似于 -

rows_generator = genSearch(SearchInfo)
row2 = next(rows_generator, None)
print row2['SearchDate']

理想情况下，我们在循环中使用迭代器，它会自动为我们做同样的事情。

Answer 2

生成器必然是迭代器，而不是迭代器。可迭代对象包含 __item__() 和 __getitem__() 方法，而迭代器包含 next() / __next__() 方法（python 版本 2.x/3.x）。