Python HDFS Snakebite：方法仅适用于打印

Question

我正在使用

的 snakebite 客户端

当我尝试在 hdfs 中创建目录或移动文件时，我注意到一个奇怪的行为。这是我的代码。它所做的只是将源目录的内容移动到目标目录。最后，显示目标目录的内容

def purge_pending(self,source_dir,dest_dir):

        if(self.hdfs_serpent.test(path=self.root_dir+"/"+source_dir, exists=True, directory=True)):
            print "Source exists ",self.root_dir+source_dir
            for x in self.hdfs_serpent.ls([self.root_dir+source_dir]):
                print x['path']
        else:
            print "Source does not exist ",self.root_dir+"/"+source_dir
            return
        if(self.hdfs_serpent.test(path=self.root_dir+"/"+dest_dir, exists=True, directory=True)):
            print "Destination exists ",self.root_dir+dest_dir
        else:
            print "Destination does not exist ",self.root_dir+dest_dir
            print "Will be created"
            for y in self.hdfs_serpent.mkdir([self.root_dir+dest_dir],create_parent=True):
                print y

        for src in self.hdfs_serpent.ls([self.root_dir+source_dir]):
            print src['path'].split("/")[-1]
            for y in self.hdfs_serpent.rename([src['path']],self.root_dir+dest_dir+"/"+src['path'].split("/")[-1]):
                print y


        for x in self.hdfs_serpent.ls([self.root_dir+dest_dir]):
            print x['path']

这是目标不存在时的示例输出

Source exists  /root/source
/root/source/208560.json
/root/source/208571.json
/root/source/208574.json
/root/source/208581.json
/root/source/208707.json
Destination does not exist /root/dest
Will be created
{'path':'/research/dest/'}
208560.json
{'path':'/research/dest/208560.json'}
208571.json
{'path':'/research/dest/208571.json'}
208574.json
{'path':'/research/dest/208574.json'}
208581.json
{'path':'/research/dest/208581.json'}
208707.json
{'path':'/research/dest/208707.json'}

奇怪的是我必须将这些打印语句放入其中，否则什么都不起作用。所以

self.hdfs_serpent.mkdir([self.root_dir+dest_dir],create_parent=True)

不起作用，但是

for y in self.hdfs_serpent.mkdir([self.root_dir+dest_dir],create_parent=True):
                print y

有！！！

也一样

self.hdfs_serpent.rename([src['path']],self.root_dir+dest_dir+"/"+src['path'].split("/")[-1])

上面的不起作用，但下面的起作用了

for y in self.hdfs_serpent.rename([src['path']],self.root_dir+dest_dir+"/"+src['path'].split("/")[-1]):
                print y

这是一个错误吗？我做错了什么吗？

Answer 1

这看起来是设计使然，因为 documentation states that most of the objects returned by the methods are generators. Therefore, the function won't usually do anything until the values have been consumed with next() 而 for 是隐含的。

Python HDFS Snakebite：方法仅适用于打印

Python HDFS Snakebite : Methods work only with print

python

hadoop

snakebite