Map reduce 的代码 python 有一个错误 'string index out of range'

Question

我的数据如下：

我想要的输出是：

 1  2  (1 occurs 2 times)
 2  4
 3  2
 4  3

为此我运行下面的代码：

SubPatent2count = {}
for line in data.split('\n'):
    for num in line.split('\t'):
        Mapper_data = ["%s\t%d" % (num[0], 1) ]
        for line in Mapper_data:
            Sub_Patent,count = line.strip().split('\t',1)
            try:
                count = int(count)
            except ValueError:
                continue

            try:
                SubPatent2count[Sub_Patent] = SubPatent2count[Sub_Patent]+count
            except:
                SubPatent2count[Sub_Patent] = count
for Sub_Patent in SubPatent2count.keys():
    print ('%s\t%s'% ( Sub_Patent,  SubPatent2count[Sub_Patent] ))

最后我得到这个错误：

     3    for num in line.split('\t'):
     4         #print(num[0])
----> 5         Mapper_data = ["%s\t%d" % (num[0], 1) ]
     6         #print(Mapper_data)
     7         for line in Mapper_data:

IndexError: string index out of range

如果您对我如何处理此错误有任何想法，请提供帮助。谢谢！

Answer 1

num[0] 可能是一个空字符串，这就是您得到索引超出范围错误的原因。另一种可能性是，您实际上是用空字符串而不是制表符分隔每行中的数字。

总之，您的代码似乎有点奇怪。例如，您将数据编码为包含一个元素 (Mapped_data) 的列表中的字符串，然后对其进行解码以对其进行处理。这真的没有必要，你应该避免它。

试试这个代码：

from collections import Counter

decoded_data = [ int(l.split(' ', 1)[0]) for l in data.split('\n') if len(l)>0]
SubPatent2count = Counter(decoded_data)

for k in SubPatent2count:
    print k, SubPatent2count[k]

Answer 2

只是建议另一种方法：您是否尝试过 itertools 中的列表理解 + groupy？

from itertools import groupby

print([(key, len(list(group))) for key, group in groupby([x.split(' ')[0] for x in data.split('\n')])])
# where [x.split(' ')[0] for x in data.split('\n')] generates a list of all starting number
# and groupy counts them

或者，如果您想要准确的输出：

from itertools import groupby

mylist = [(key, len(list(group))) for key, group in groupby([x.split(' ')[0] for x in data.split('\n')])]


for key, repetition in mylist:
    print(key, repetition)

Answer 3

谢谢大家，你们的建议对我很有帮助，我改了代码如下：

SubPatent2count = {}
for line in data.split('\n'):
Mapper_data = ["%s\o%d" % (line.split(' ')[0], 1) ]
    for line in Mapper_data:
            Sub_Patent,count = line.strip().split('\o',1)
            try:
                count = int(count)
            except ValueError:
                continue

            try:
                SubPatent2count[Sub_Patent] = SubPatent2count[Sub_Patent]+count
           except:
                SubPatent2count[Sub_Patent] = count
for Sub_Patent in SubPatent2count.keys():
    print ('%s\t%s'% ( Sub_Patent,  SubPatent2count[Sub_Patent] ))

结果如下：

1  2  (1 occurs 2 times)
2  4
3  2
4  3

Map reduce 的代码 python 有一个错误 'string index out of range'

Map reduce's code python with an error 'string index out of range'

python

reduce

dictionary