Question

我正面临类似的问题，另一位用户@AMisra发布了一段时间，但没有收到明确答案。问题是因为我使用的是第三方代码而无法对其进行太多修改。我有一个在代码中多次调用的函数来创建子进程，将数据写入stdin然后读取。它只是挂在这一行

line = self.classifier.stderr.readline()

请注意，我无法使用communicate：由于func2(classifier, vectors)需要多次调用，因此会引发异常。

import subprocess
import paths
import os.path

class CRFClassifier:
    def __init__(self, name, model_type, model_path, model_file, verbose):
        self.verbose = verbose
        self.name = name
        self.type = model_type
        self.model_fname = model_file
        self.model_path = model_path

        if not os.path.exists(os.path.join(self.model_path, self.model_fname)):
            print 'The model path %s for CRF classifier %s does not exist.' % (os.path.join(self.model_path, self.model_fname), name)
            raise OSError('Could not create classifier subprocess')


        self.classifier_cmd = '%s/crfsuite-stdin tag -pi -m %s -' % (paths.CRFSUITE_PATH, 
                             os.path.join(self.model_path, self.model_fname))
#        print self.classifier_cmd
        self.classifier = subprocess.Popen(self.classifier_cmd, shell = True, stdin = subprocess.PIPE, stderr = subprocess.PIPE)

        if self.classifier.poll():
            raise OSError('Could not create classifier subprocess, with error info:\n%s' % self.classifier.stderr.readline())

        #self.cnt = 0


    def classify(self, vectors):
#        print '\n'.join(vectors) + "\n\n"

        self.classifier.stdin.write('\n'.join(vectors) + "\n\n")

        lines = []
        line = self.classifier.stderr.readline()
        while (line.strip() != ''):
#            print line
            lines.append(line)
            line = self.classifier.stderr.readline()


        if self.classifier.poll():
            raise OSError('crf_classifier subprocess died')

        predictions = []
        for line in lines[1 : ]:
            line = line.strip()
#            print line
            if line != '':
                fields = line.split(':')
#                print fields
                label = fields[0]
                prob = float(fields[1])
                predictions.append((label, prob))

        seq_prob = float(lines[0].split('\t')[1])

        return seq_prob, predictions


    def poll(self):
        """
        Checks that the classifier processes are still alive
        """
        if self.classifier is None:
            return True
        else:
            return self.classifier.poll() != None

为输入文件创建分类器对象，该文件是具有句子列表的文档，并且在创建时它还使用该句子列表执行外部命令。然后在单独的函数中处理每个句子，为每个句子提供单独的向量。这个新向量将传递给分类函数。

def func2():
    classifier=create a classifier object for an input file, this executes the external command
    for sentence in sentences:
        vectors=process(sentence)# some external function
        classifier.classify(features)

Answer 1

在self.classifier方法而不是构造函数中初始化classify，并使用Popen()。还需要使用stdout而不是stderr。

popen与python在python2.7中读取和写入块

1 个答案: