Java calling Python function using PythonInterpreter

Question

I have a python module auth.py:

keys= {
 "s1": ["k1", "k2"],
 "s2": ["k1", "k2"]
}
def get_keys_by_name(name):
 return keys[name]

And the calling Java code:

String keyname= "somename"
interpreter.exec("from services.framework import auth");
List<String> keys = (List<String>) interpreter
 .eval("auth.get_keys_by_name(" + keyname+ ")");

Each time i call the code i get a NameError form the argument (keyname) that i try to pass to the python code.

Anyone knows what i am doing wrong?

• Thomas: Maybe quotes are missing? If it where a Java call you'd do something like getKeysByName("abc") while your code looks more like getKeysByName(abc).
• Gobliins: well name is variable in my jav code, sorry if it wasnt clear. I have put it also in the code
• Gobliins: but i think you are right, you can put this as answer

Answer 1

As per request my comment as an answer :)

Passing a key with value abc to eval("auth.get_keys_by_name(" + keyname+ ")") would result in auth.get_keys_by_name(abc) being evaluated, i.e. the interpreter will probably look for a variable named abc and since that doesn't exist your get a NameError.

Adding quotes (I'm no python expert so I don't know whether single or double quotes would be better) should fix that, i.e. eval("auth.get_keys_by_name(\"" + keyname + "\")") would evaluate auth.get_keys_by_name("abc").

• Karl Knechtel: The Python answer to "should I use single or double quotes" is "whichever makes your life easier" (i.e., requires less escaping), in general. IMO, this is still true when you're embedding the Python code in some other-language code. :)

Answer 2

I think that your problem is that the python interpreter is interpreting the java variable keyname as a Python variable within the python program rather than as a string. Add quotes to around keyname and you won't get this error. I other words

Instead of using:

List<String> keys = (List<String>) interpreter
 .eval("auth.get_keys_by_name(" + keyname+ ")");

Use this:

List<String> keys = (List<String>) interpreter
 .eval("auth.get_keys_by_name('" + keyname+ "')");