Re: [Py4j-users] How to access attributes ?

[Wilfried F. <wil...@gm...>]

Hi,

thank you for your fast answer !

I added : c = gateway.get_field(stack, 'test3')
but then it raises :

Traceback (most recent call last):
  File "test.py", line 22, in <module>
    main()
  File "test.py", line 18, in main
    c = gateway.get_field(stack, 'test3')
  File "/usr/lib/python2.7/site-packages/py4j/java_gateway.py", line
538, in __call__
    self.target_id, self.name)
  File "/usr/lib/python2.7/site-packages/py4j/protocol.py", line 304,
in get_return_value
    format(target_id, '.', name, value))
py4j.protocol.Py4JError: An error occurred while calling t.get_field. Trace:
py4j.Py4JException: Method get_field([class py4j.examples.Stack, class
java.lang.String]) does not exist
at py4j.reflection.ReflectionEngine.getMethod(ReflectionEngine.java:333)
at py4j.reflection.ReflectionEngine.getMethod(ReflectionEngine.java:342)
at py4j.Gateway.invoke(Gateway.java:252)
at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:133)
at py4j.commands.CallCommand.execute(CallCommand.java:79)
at py4j.GatewayConnection.run(GatewayConnection.java:207)
at java.lang.Thread.run(Thread.java:745)

and auto_field=True returns <py4j.java_gateway.JavaMember object at
0x7f2d7ce7aa10>

I am using : pip2.7 show py4j
---
Name: py4j
Version: 0.8.2.1
Location: /usr/lib/python2.7/site-packages
Requires:

and

java version "1.7.0_71"
OpenJDK Runtime Environment (IcedTea 2.5.3) (Arch Linux build
7.u71_2.5.3-1-x86_64)
OpenJDK 64-Bit Server VM (build 24.65-b04, mixed mode)

Thank you.

On Thu, Dec 4, 2014 at 5:23 AM, Barthelemy Dagenais
<bar...@in...> wrote:
> Hi!
>
> Thanks for using Py4J!
>
> To access fields, you can either use gateway.get_field(object, "test1") or
> set auto_field=True when initializing the gateway to access object.test1.
>
> Reference: http://py4j.sourceforge.net/faq.html#how-to-access-a-field
>
> auto_field is False by default because it costs an extra lookup.
>
> Barthelemy
>
> On Wed Dec 03 2014 at 10:30:12 PM Wilfried Fauvel
> <wil...@gm...> wrote:
>>
>> Hi, I am testing py4j and I would like to know if it is possible to
>> access class attributes.
>> In the Stack class from the getting started page, I added :
>>
>>     public static final String test1 = "TEST";
>>     public static final int test2 = 12;
>>     public int test3 = 12;
>>
>> and with python 2.7 :
>>
>> gateway = JavaGateway()
>> stack = gateway.entry_point.getStack()
>> print(gateway.help(stack))
>> >>> field section is empty
>>
>> print stack.test1
>> print stack.test2
>> print stack.test3
>> >>> <py4j.java_gateway.JavaMember object at 0x7fd7b1647250>
>> >>> <py4j.java_gateway.JavaMember object at 0x7fd7b1647a10>
>> >>> <py4j.java_gateway.JavaMember object at 0x7fd7b16479d0>
>>
>> Thank you,
>> Wilfried.
>>
>>
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