examples: add an example of a simple process wrapper, built around an…

… interactive python process, in wrapping_interactive_python.v

examples/process/wrapping_interactive_python.v

@@ -0,0 +1,44 @@
+import os
+import time
+import term
+
+python_exe := os.find_abs_path_of_executable('python') or {
+	eprintln('This example needs a python executable in your PATH. Please install Python to see it in action.')
+	exit(1)
+}
+mut p := os.new_process(python_exe)
+defer {
+	dump(p.code)
+	p.close()
+	p.wait()
+}
+// The Python flags here, are needed to reduce clutter and buffering.
+// See https://docs.python.org/3/using/cmdline.html
+p.set_args(['-i', '-q', '-u'])
+p.set_redirect_stdio()
+p.run()
+dump(p.pid)
+println('This is a simple V wrapper/shell for the Python interpreter.')
+println('Try typing some python code here, or type `bye` to end your session:')
+for p.is_alive() {
+	// check if there is any input from the user (it does not block, if there is not):
+	if os.fd_is_pending(0) {
+		cmd := os.get_raw_line()
+		if cmd.len == 0 {
+			println('closed stdin detected, perhaps due to Ctrl-D...exiting')
+			break
+		}
+		if cmd.trim_space() == 'bye' {
+			println('Goodbye...')
+			break
+		}
+		p.stdin_write(cmd)
+	}
+	if oline := p.pipe_read(.stdout) {
+		print(term.bright_yellow('python stdout: ') + term.bold(oline))
+	}
+	if eline := p.pipe_read(.stderr) {
+		eprint(term.red('python stderr: ') + eline)
+	}
+	time.sleep(20 * time.millisecond)
+}