我有以下代码:
def get_input(self):
"""
Reads command from stdin, returns its JSON form
"""
json_string = sys.stdin.read()
print("json string is: "+json_string)
json_data =json.loads(json_string)
return json_data
def accept_commands(self):
while True:
json_data = self.get_input()
command = self.command_analyzer.is_command(json_data) # Check wether the command exists. Return it if it does
#The command exists
if command is not None:
#The addon is not currently active
if analyzer.intent(json_data) not in self.active_addons:
self.activate_addon(command,json_data)
#The addon is active and so we need to send the data to the subprocess
else:
self.communicate_with_addon(command,json_data,json_string)
它读取从另一个进程发送给它的 json 字符串。 json 是从 stdin 读取的。 由于某种原因，我得到以下输出:
json string is: <Some json here>
json string is:
Traceback (most recent call last):
File "/Users/Matan/Documents/workspace/ProjectSH/addonmanager/addon_manager.py", line 63, in <module>
manager.accept_commands()
File "/Users/Matan/Documents/workspace/ProjectSH/addonmanager/addon_manager.py", line 49, in accept_commands
json_data = self.get_input()
File "/Users/Matan/Documents/workspace/ProjectSH/addonmanager/addon_manager.py", line 42, in get_input
json_data =json.loads(json_string)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/__init__.py", line 338, in loads
return _default_decoder.decode(s)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/decoder.py", line 365, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/decoder.py", line 383, in raw_decode
raise ValueError("No JSON object could be decoded")
json 是从以下位置发送的:
class MessageReceiver:
def __init__(self):
'''
Connect to the AMQP broker and starts listening for messages.
Creates the a Popen object to pass command info to the addon_manager script (which
is in charge of managing scripts)
'''
addon_manager_path = configuration.addon_manager_path()
addon_manager_path = os.path.join(addon_manager_path,'addon_manager.py')
execute = "python " + addon_manager_path
self.addon_manager = subprocess.Popen(execute, stdin=subprocess.PIPE, shell=True)
self.component_name= configuration.get_attribute("name")
if len(sys.argv)>1:
host_ip = sys.argv[1]
else:
host_ip = 'localhost'
#Start a connection to the AMQP server
self.connection = pika.BlockingConnection(pika.ConnectionParameters(host=host_ip))
#Create a channel to the server
self.channel = self.connection.channel()
self.channel.queue_declare(queue="kitchen")
#callback method to be called when data is received
#It sends the data that is received by the client to the addon_manager
def data_received(ch, method, properties, body):
##TODO: Might want to add some checks. Is body a JSON? etc.
print("writing data to addon_manager")
self.addon_manager.communicate(body)
self.channel.basic_consume(data_received,queue='kitchen',no_ack=True)
self.channel.start_consuming()
这里出了什么问题？
最佳答案
默认情况下，stdin.read() 会阻塞，直到读取整个缓冲区。如果您只能解码一个 JSON 对象，那么这就是在 stdin 被另一进程关闭之前发送的所有内容。
如果您需要流式传输多个 JSON block ，您应该
a) 不关闭写入过程中的流，并且 b) 不要在 Python 中进行阻塞读取。
改为分块或按行读取；请参阅Loading and parsing a JSON file with multiple JSON objects in Python和 How do I use the 'json' module to read in one JSON object at a time?了解读取行分隔或多行的 JSON 对象的技术。
您可以调整其中之一来生成生成器函数；您可以对其进行循环以一次生成一个 JSON 对象，并在中间阻塞以等待下一个 JSON 对象:
def get_input(self):
for line in sys.stdin:
yield json.loads(line)
和
def accept_commands(self):
for json_data in self.get_input():
# do something with `json_data`
您正在使用Popen.communicate()写入管道。这会在写入后关闭管道，然后等待进程终止。
如果您希望管道保持打开状态，请不要使用 Popen.communicate 而是直接写入 Popen.stdin pipe .
关于python - 为什么 `stdin.read()` 不读取整个缓冲区？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25483684/