Missing attributes in imported class in Jython

Question

I declared a Java class -

class Beach {
    private String name, city;

    public Beach(String name, String city) {
        this.name = name;
        this.city = city;
    }
}

I imported this into jython and tried to create an object -

import Beach
b = Beach("candolim", "goa")


Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: java.lang.Object(): expected 0 args; got 2

Where is my two argument constructor?

Edit:

I follow these exact steps -

// Comment - Remove all files from directory to not create any confusion.
$ rm -rf *

$ vi Beach.java

class Beach {
private String name, city;

public Beach(String name, String city) {
  this.name = name;
  this.city = city;
 }
}

$ javac *.java
$ javap Beach

Compiled from "Beach.java"
class Beach {
  public Beach(java.lang.String, java.lang.String);
}


$ jython
>>> import Beach
>>> b = Beach()
>>> dir(b)

['__class__', '__copy__', '__deepcopy__', '__delattr__', '__doc__', '__eq__', '__format__', '__getattribute__', '__hash__', '__init__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__str__', '__subclasshook__', '__unicode__', 'class', 'equals', 'getClass', 'hashCode', 'notify', 'notifyAll', 'toString', 'wait']

So Beach is a class in module Beach? import Beach.Beach does not work. `ImportError: No module named Beach ` — Kshitiz Sharma, May 23 '13 at 11:21
I've worked with Python. `from Beach import Beach` does not work. Neither does `import Beach` and `b = Beach.Beach()` — Kshitiz Sharma, May 23 '13 at 11:26

mzjn · Accepted Answer · 2013-05-31T08:03:06.393

It looks like you are not using the Java class shown in the question. I can reproduce the error.

beach.py:

import Beach

b = Beach("candolim", "goa")
print b.__class__

Beach.java alt. 1 (zero constructor arguments):

public class Beach {
  private String name, city;

  public Beach() {
  }
}

Output when using Beach.java alt. 1:

$ jython beach.py
Traceback (most recent call last):
  File "beach.py", line 3, in <module>
    b = Beach("candolim", "goa")
TypeError: Beach(): expected 0 args; got 2

Beach.java alt. 2 (the class in the question; two arguments):

public class Beach {
private String name, city;

public Beach(String name, String city) {
  this.name = name;
  this.city = city;
 }
}

Output when using Beach.java alt. 2:

$ jython beach.py
<type 'Beach'>

Edit: something strange seems to be going on. Here is what happens when I try to follow the steps in the edited question:

$ rm *.class
$ cat Beach.java
public class Beach {
    private String name, city;

    public Beach(String name, String city) {
        this.name = name;
        this.city = city;
    }
}
$ javac Beach.java
$ javap Beach
Compiled from "Beach.java"
public class Beach {
  public Beach(java.lang.String, java.lang.String);
}
$ jython
Jython 2.7b1 (default:ac42d59644e9, Feb 9 2013, 15:24:52)
[Java HotSpot(TM) 64-Bit Server VM (Oracle Corporation)] on java1.7.0_15
Type "help", "copyright", "credits" or "license" for more information.
>>> import Beach
>>> b = Beach()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Beach(): expected 2 args; got 0
>>>

Note that the javap output is different. Here it says public class Beach. In the question it is just class Beach.

Maybe OP didn't recompile the java file after adding arguments to the constructor? — Geoff Gerrietts, May 23 '13 at 18:34
@mzjn The problem was that Beach was not public as you said. Many thanks mzjn. — Kshitiz Sharma, May 31 '13 at 09:09
I wish that python would provide a descriptive error message instead of just instantiating a dummy object. — Kshitiz Sharma, May 31 '13 at 09:11

Missing attributes in imported class in Jython

1 Answers1