Python's method of calling executable file __python

Recently I used Python to call C programs, so I looked at the way Python calls other programs. Generally speaking, Python calls C/C + + There are two ways, one is to invoke the dynamic link library, that is, the so file, a C-generated executable file. Specifically, depending on the application scenario.

Python invokes the executable file, and in fact executes the commands that were originally executed on the command line in Python.

Specific methods:

(1). Write C + + program with main program MAIN.C

#include <stdio.h>
#include <stdlib.h>
int main () {
    int a = ten;
    int b = 3;


    int c = A * b;
	printf ("%d\n", c);
    return 0;
}

Save the program and compile it into an executable file with GCC Calledbypy.

(2). Python Calling Program

(This program is from http://www.cnblogs.com/apexchu/p/5015961.html)

Import commands  
import os  
main = "./calledbypy"  
if Os.path.exists (main):  
    rc, out = Commands.getstatusoutput (main)  
    print ' rc =%d, \nout =%s '% (RC, out)  
  
print ' * ' *10  
f = os.popen (main)    
dat A = F.readlines ()    
f.close ()    
print data  
  
print ' * ' *10  
r_v = Os.system (main) 

The results after execution are:

rc = 0,
out = 30
**********
[' 30\n ']
**********
30
0

There are 3 ways to invoke an executable file in a Python program. commands, Popen and Os.system. From the above output can be seen:

Commands.getstatusoutput () Saves the print value and the return value of the main function in the executable program, but does not print the output in the execution of the command, and then writes the print statement.

Popen prints all of the printed content in the executable program to a file, does not print the content to be output during execution, and can output all the printed content by reading the file, and Os.popen does not save the return result of the main function;

Os.system () saves the printed value and the return result of the main function, and prints the content to be printed during execution.

As mentioned above, these three methods are actually executing commands in Python, so they are not just used to execute executable files, they can also be used to execute other instructions on the Linux system.

For example

Import commands
import os


main = "ls"
rc, out = Commands.getstatusoutput (main)
print RC
print out< C5/>print ' * ' *
f = os.popen (main)
data = F.readlines ()
f.close ()
print data


print ' * '
* R_v = Os.system (main)
print R_v
 

The output results are:

0
Calledbypy
Calledbypy.c
Makefile
pycallcpp.py
**********
[' calledbypy\n ', ' calledbypy.c\n ', ' makefile\n ', ' pycallcpp.py\n ']
**********
Calledbypy
Calledbypy.c
Makefile
pycallcpp.py
0