How to pass the java parameter to python , Call Python code from Java

Question

I create simple python statement my_utils.py

def adder(a, b):
    c=a+b
    return c

I would like to assign value to python in Java.

public class ParameterPy {
public static void main(String a[]){
try{

int number1 = 100;
int number2 = 200;

ProcessBuilder pb = new ProcessBuilder("C:/Python27/python","D://my_utils.py",""+number1,""+number2);
Process p = pb.start();

BufferedReader bfr = new BufferedReader(new InputStreamReader(p.getInputStream()));

System.out.println(".........start   process.........");  
String line = "";     
while ((line = bfr.readLine()) != null){
    System.out.println("Python Output: " + line);
}
System.out.println("........end   process.......");


}catch(Exception e){System.out.println(e);}
}
}

However, process builder is not able to pass the parameter value to a, b in python and display the result.

How to give the parameter value to python? If the numeric value is worked? How about if I pass the non-numeric value such as a string to python

def str(myWord):
    if myWord=="OK":
        print "the word is OK."
    else:
        print " the word is not OK."

Possible duplicate of stackoverflow.com/questions/27235286/… — hammerfest
– hammerfest, Commented Oct 6, 2016 at 7:21
You got the input stream from the process, not the output stream that is where the print statements are written to — OneCricketeer
– OneCricketeer, Commented Oct 6, 2016 at 7:27

greene · Accepted Answer · 2016-10-06 08:43:36Z

2

The Python sys module provides access to any command-line arguments via the sys.argv. But the type of arguments is string always. Here is the example how I would like to check numeric values:

import sys

print 'Number of arguments:', len(sys.argv), 'arguments.'
print 'Argument List:', str(sys.argv)

def adder(a, b):
    c=a+b
    return c

def is_number(x):
    try:
        float(x)
        return True
    except ValueError:
        return False

p1 = sys.argv[1]
p2 = sys.argv[2]

if is_number(p1) and is_number(p2):
    print "Sum: {}".format(adder(float(p1), float(p2)))
else:
    print "Concatenation: {}".format(adder(p1, p2))

UPDATED: As @cricket_007 mentioned, you can use isdigit if you want to check integers only. But it does not work for float:

>>> "123".isdigit()
True
>>> "12.3".isdigit()
False

edited Oct 6, 2016 at 8:43

answered Oct 6, 2016 at 7:21

greene

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2 Comments

OneCricketeer Over a year ago

Doesn't the python string class provide isdigit? Why try to cast the value?

greene Over a year ago

isdigit() is also OK if you expect integers only. But it returns False for float.

bob90937 · Accepted Answer · 2016-10-06 09:13:25Z

import sys
# print sys.argv

print "sys.argv is:",sys.argv
# ['D://my_utils.py', '100', '200', 'google']

a= sys.argv[1]
b= sys.argv[2]
print "a is:", a
print "b is:", b
a= int (a)
b= int(b)

def adder(a, b):
    c=a+b
    return c

print adder(a,b)

searchTerm=sys.argv[3]
print searchTerm  ##google

def word(searchTerm):
    if searchTerm=="google":
        print " you get it"
    else:
        print " the word is different."

word(searchTerm)

in java

int number1 = 100;
int number2 = 200;
String searchTerm="google";
ProcessBuilder pb = new ProcessBuilder("C:/Python27/python","D://searchTestJava//my_utils.py",""+number1,""+number2,""+searchTerm);
Process p = pb.start();

BufferedReader bfr = new BufferedReader(new InputStreamReader(p.getInputStream()));

System.out.println(".........start   process.........");  
String line = "";     
while ((line = bfr.readLine()) != null){
    System.out.println("Python Output: " + line);

the output result:

Python Output: a is: 100
Python Output: b is: 200
Python Output: 300
Python Output: google
Python Output:  you get it

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