Added an example for how conditional control flow of a cmd2 application can be achieved via the py command and python scripts.

1 files changed, 102 insertions, 0 deletions

diff --git a/examples/python_scripting.py b/examples/python_scripting.py
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+#!/usr/bin/env python
+# coding=utf-8
+"""A sample application for how Python scripting can provide conditional control flow of a cmd2 application.
+
+cmd2's built-in scripting capability which can be invoked via the "@" shortcut or "load" command and uses basic ASCII 
+text scripts is very easy to use.  Moreover, the trivial syntax of the script files where there is one command per line
+and the line is exactly what the user would type inside the application makes it so non-technical end users can quickly
+learn to create scripts.
+
+However, there comes a time when technical end users want more capability and power.  In particular it is common that
+users will want to create a script with conditional control flow - where the next command run will depend on the results
+from the previous command.  This is where the ability to run Python scripts inside a cmd2 application via the py command
+and the "py run('myscript.py')" syntax comes into play.
+
+This application and the "script_conditional.py" script serve as an example for one way in which this can be done.
+"""
+import os
+
+from cmd2 import Cmd, options, make_option, CmdResult, set_use_arg_list
+
+# For option commands, pass a list of argument strings instead of a single argument string to the do_* methods
+set_use_arg_list(True)
+
+
+class CmdLineApp(Cmd):
+    """ Example cmd2 application to showcase conditional control flow in Python scripting within cmd2 aps. """
+
+    def __init__(self):
+        Cmd.__init__(self)
+        self._set_prompt()
+
+    def _set_prompt(self):
+        """Set prompt so it displays the current working directory."""
+        self.prompt = '{!r} $ '.format(os.getcwd())
+
+    def postcmd(self, stop, line):
+        """Override this so prompt always displays cwd."""
+        self._set_prompt()
+        return stop
+
+    # noinspection PyUnusedLocal
+    @options([], arg_desc='<new_dir>')
+    def do_cd(self, arg, opts=None):
+        """Change directory."""
+        # Expect 1 argument, the directory to change to
+        if not arg or len(arg) != 1:
+            self.perror("cd requires exactly 1 argument:", traceback_war=False)
+            self.do_help('cd')
+            self._last_result = CmdResult('', 'Bad arguments', '')
+            return
+
+        # Convert relative paths to absolute paths
+        path = os.path.abspath(os.path.expanduser(arg[0]))
+
+        # Make sure the directory exists, is a directory, and we have read access
+        out = ''
+        err = ''
+        war = ''
+        if not os.path.isdir(path):
+            err = '{!r} is not a directory'.format(path)
+        elif not os.access(path, os.R_OK):
+            err = 'You do not have read access to {!r}'.format(path)
+        else:
+            try:
+                os.chdir(path)
+            except Exception as ex:
+                err = '{}'.format(ex)
+            else:
+                out = 'Successfully changed directory to {!r}\n'.format(path)
+                self.stdout.write(out)
+
+        if err:
+            self.perror(err, traceback_war=False)
+        self._last_result = CmdResult(out, err, war)
+
+    @options([make_option('-l', '--long', action="store_true", help="display in long format with one item per line")],
+             arg_desc='')
+    def do_dir(self, arg, opts=None):
+        """List contents of current directory."""
+        # No arguments for this command
+        if arg:
+            self.perror("dir does not take any arguments:", traceback_war=False)
+            self.do_help('dir')
+            self._last_result = CmdResult('', 'Bad arguments', '')
+            return
+
+        # Get the contents as a list
+        contents = os.listdir(os.getcwd())
+
+        fmt = '{} '
+        if opts.long:
+            fmt = '{}\n'
+        for f in contents:
+            self.stdout.write(fmt.format(f))
+        self.stdout.write('\n')
+
+        self._last_result = CmdResult(contents, '', '')
+
+
+if __name__ == '__main__':
+    c = CmdLineApp()
+    c.cmdloop()